The only time I've restarted was in time attack mode on Snaefell Mountain --more times than I'd care to admit-- and that never had any issues. I've been running career mode lately but trying very hard and so far sticking to a never-restart policy despite not having practice sessions(and boy am I taking some lumps for it
).
Taking a break from racing so I have some time to write a typical TL;DR post.
Some career mode observations after about a season and a half:
I don't have a problem with the way the career is generally set up overall, as long as you do eventually get invited to the big dance. The devs said in the patch notes they made it easier to get invitations to the TT event, so hopefully that will come as I progress. The tracks are all pretty and okay to drive(most are less bumpy than the big track). Most races are pretty short, but some of them can be much longer. You can make money quite quickly if you ride fairly well and don't crash, but there is at least some risk of career failure if you wreck too much without some wins to pay for the repairs. It has a section in your budget for Repairs but actual bike repair costs seem to all be filed as Maintenance. It would be nice if you got a message to let you know you've unlocked a manufacturer discount or unlocked the other bikes at the shop - as it is you just have to go check for yourself.
I did have one issue where I accidentally accepted a superbike event and I wasn't able to change it back to the supersport option(actually I did, but then switched back to superbike and it got stuck) so I had to withdraw from that one. I also am the extreme opposite of a big fan of the game saving your progress every lap(and every section on Snaefell Mountain). It is a completely unwanted feature for me, and you can restart every race anyway(most are pretty short to boot) so I don't see the need. I'm not sure if it's like this for everybody, but in my case the game briefly freezes when it saves - sometimes for just a tenth of a second, sometimes longer, very occasionally for a full second or more. Has already caused me at least one crash and even when it doesn't I find it very off-putting. That's about it for my main complaints, notwithstanding the AI sometimes running you over(sometimes avoiding you quite well) or trying to turn through you or being really slow when unfortunately right in front of you. Bots will be bots.
I am finding it incredibly difficult to get a gauge on how fast the AI is going to be on any track in career so far. Their overall times for each race can easily vary by upwards of 30 seconds for each rider/bike. I can only see their fastest laps if I don't have a faster one, but those seem to vary greatly too. Even for the same bike/rider. I've recorded an awful lot of numbers for the various tracks but I haven't been able to learn much about how fast to expect them to be. I'm not sure I've even seen how fast they can really go at a lot of places. I'm not seeing much clear difference between rank B and C events, either in pace or in what riders show up.
It does say that each rider has their own skill levels, but I'm seeing huge variations even among the [I think] lower-skilled riders(I know some of the real-world faster riders but I'm no expert on the road racing scene). To the point that I'll be able to just eat them up in one race and be only a little faster on a good lap in another. I had James Hillier in one event destroy everybody and run 10 seconds faster per lap than anyone else had in earlier races, but then a later event at the same track a guy who I've generally destroyed(Kenny Parov) ran only about 2 seconds off that pace. The one time I saw Michael Dunlop he was waaaaay at the back.
I've definitely noticed that in multi-round events they are nearly always dramatically quicker in the later rounds than the first one. It also seems like they are usually easier to beat in TT-style events than in races, even accounting for the fact I'm much more experienced on the Snaefell TT stages than the other tracks(I'm usually at least close to the top in all TTs). They unfortunately seem generally terrible at most sections of Snaefell Mountain. I've never yet seen a top 3-4 overall TT event time come from any group other than the one I was in, although I have seen the best time for an individual bike be much faster than that bike's best in my group.
Other than that top overall result observation, I'm not sure I've noticed any particular pace difference between the riders in my group and the ones from other groups(who's times are obviously faked). I'd like to assume that the riders in my group are more or less "real" times taken from their actual AI-driven runs, but only the rider immediately before me starts the race from the start line, so there is obviously a certain amount of fakery happening if I start late in my group.
I've only been given one full-lap TT at Snaefell Mountain so far(one lap training) and I did pretty good at that, only 3 crashes and won by a mile. There's a lot of 2-3 section TT runs there. Almost all of my wins have come on that track because I still crash too much at the others. I think I've only won one individual mass-start race. I've led a couple multi-round TT events but always blow it. I did just now technically win one TT event, but it was a stupid and unusual one that shouldn't count. It was a one-round TT against only one other rider and he was horrid. I drove one of my poorest recent races, crashed multiple times and gained 15 seconds on him on my one good third lap to win. All of the other TT events have had from 5-30 opponents.
This is all on Supersport bikes with difficulty on Medium. I've read that the difficulty doesn't actually affect their performance, so I did do one quick test on a short race in quick race mode and they were much tougher, both on track and on the timing sheet, on Expert than they were on Medium, but with as much variance as I've seen in career that might not mean a lot. Or maybe the difficulty just doesn't affect career mode, I've never changed it there.