Known issue.
The developers made changes to prevent some exploits, though what precisely they were wasn’t ever defined.
The swirly, the funky hero levelling thing, hopefully they do find ways to address it which don’t impact things quite so strangely.
Titan damage though, that’s been just fine: no noticible slow down on tile movement on raids or titans or map (on the rare time I don’t autoplay). 20k to 10k or whatever is an easy combination of titan color, titan level, and plain jane board randomness.