(This is an unmodded SC issue)
SCVs will attempt to repair Zerg (and possibly Protoss? couldn't seem to reproduce this on a T+P base over a few minutes) units and buildings of the same AI Player they're owned by periodically, which makes them stand idly for an unspecified amount of time. They eventually go back to mining, however if the AI needs to mine or has Terran units pending repair this deteriorates the AI's performance.
(For posterity: a fix for this was once deployed for 1.16 in teippi, commit here
Repro:
- Boot up any mod with AISE or 1.16 or Remastered
- Launch To Slay the Beast, xZ8, from the Expansion Campaign menu
- Speed up the game (if possible, with the AI debug plugin for example) and observe as SCVs in Orange/White bases periodically stop mining

(This is an unmodded SC issue)
SCVs will attempt to repair Zerg (and possibly Protoss? couldn't seem to reproduce this on a T+P base over a few minutes) units and buildings of the same AI Player they're owned by periodically, which makes them stand idly for an unspecified amount of time. They eventually go back to mining, however if the AI needs to mine or has Terran units pending repair this deteriorates the AI's performance.
(For posterity: a fix for this was once deployed for 1.16 in teippi, commit here
Repro: