Hello! I solved the problem for PC1 and PC2! I further investigate the problem. And so came to this conclusion.
GTA: San Andreas I have a standard 1.0 with no mods.
The problem was in the shadows, which appeared to have Visual FX to put the texture quality to the level of "Medium". Antialiasing does not play any role in this issue. In any case, I conducted an experiment by exposing Antialiasing with step 1 (1, 2, 3).
Problem occurred in a single player and in the MTA. I think in SA there are some objects that are improperly charged the shade, so is the effect of the wave.
Resolve: Visual FX: texture quality to the level of "Low".
Sounds good! Since GTA:SA is from 2005, I would think that your PC1 is fast enough to run it at highest settings with no lag, but I guess not. Thank you for posting your results.