There are some users of the AVCHD format with playback issues in 2022. This is a completely rebuilt underlying color system among other changes, and it does seem to tax most systems more heavily.
For this, it would be good to post this in detail giving your computer specs, media specs, and playback issues on their Premiere Pro UserVoice system. That would get the information directly into the engineer's system.
Sorry for the frustration with the performance of this format. May I request that you download the Beta version of Premiere Pro and test your clips' performance there? There are improvements to specific Long GOP formats in this Beta version that might apply to your media. If your media is performant in Beta, it will also be the same in an upcoming version of Premiere Pro, so I'm eager to find out if you will be better off shortly.
If you do not want to download the Beta or test, you can leave us with a sample clip, and we'll be happy to test the media for you. I hope we can help you, Rahoul.