I'm not sure if this has been reported before, but ever since update 1.26, I have been experiencing freezes/stutters while playing GT7 in a PS4.
I first noticed it when playing in Sport mode, as it was what I mostly played until recently, the game would freeze for about 1.5 to 2 seconds, and then would resume, with me having fallen behind 1.5 to 2 seconds. This became very frustrating in the recent competitions where I would lose more than a minute in accumulated freezes.
So I quit Sport mode for now, but I also started experiencing it in campaign mode (forgot the actual name of the mode), sure it freezes, but since it is against AI and offline, I don't fall behind in the race, so I just have to have patience.
I brought this up on reddit wondering if others had experienced this, and what I learned is that it's not occurring with any PS5 owner, but solely with PS4s, even the PS4 pros. About 7 other people mentioned experiencing this occasional freeze, even in Multiplayer mode. PS5 owners did mention enjoying the positions they gained from seeing people suddenly disappear and reappear behind them in a race.
So I tried to troubleshoot it, thinking it might be because I have an HDD and the game might be reading too slow. I then ordered a 2TB SSD, fresh install of the PS4 firmware, fresh install of GT7 and still experience the same problem. Since I originally experienced it while playing online, I changed my PS4 from 2.4Ghz Wifi to Lan 1Gbps connection with my router. Still the same problem.
I see this freezing occur more often when I go over the finish line and my lap times are updated, but the freezing can occur anywhere in the track, in any track, even when you are just trying to do time attack with no other cars in the track.
I tried to find a way to contact Polyphony Digital to report the bug but, no way to contact them, japanese companies are really obtuse with their customer service. I did reach out to a Playstation customer service representative and reported the bug to them in hopes they might be able to pass it along to Polyphony Digital and it not end in a pile of papers in the garbage bin.
But for now, it seems GT7 in the PS4 for many is just broken if you wish to compete online.