stickwar3://watchReplay?guid=40d6285b-2546-fc83-8903-e3966b630000
Try watching the above replay and make it to the end (around 12 mins mark). The frame rate progressively worsens and everyone else in the game already disconnected.
It feels like the effects on units that have been killed and aren't on the battlefield anymore are still being processed, thus lowering FPS. The heal spell doesn't disappear and the sudden death animations were skipped completely, probably due to lag on the server.