Since the 1.28 title update, GTA 5 PC players have reported low frame rate in the game since the latest update on Rockstar’s support site.
We have received reports of lower framerate in GTAV and GTA Online after Title Update 1.28 on PC, and we are looking into these reports now.
On Facebook, the creators of a popular GTA V mod called LCPD First Response said that the problem was caused by the new anti-modding measures that were allegedly added in the new update. Players have reported their game going as slow as 3 fps while using the LCPD First Response mod.
Although Rockstar is ok with single-player mods, but GTA online mods and frowned upon.
“Our primary focus is on protecting GTA Online against modifications that could give players an unfair advantage, disrupt gameplay, or cause griefing.”
So it’s a possibility that the single-player mods are being affected by the measures taken to prevent modding online.