replay hangs on upper bound increase

[covert edge]

in https://discord.com/channels/860665589738635336/1459822192786411700 you have fixed the worst hang problem: on every 100 border crossing.
Current one is of same kind: replay hangs every time upper bound is in process of increase (visual ticking +100 up, redrawing progressbar...). Current playback position is hundreds of ticks away from upper bound, "having nothing to play yet" is not the case.

To be able to really debug movement, I have to wait for full replay to be processed, otherwise it's not clear if this small creep hang from my algorithm, or from upper bound lag.

also I've started utilising Stop more because of it. There's a bug there too: last segment of replay, when Stop used, does not contain data: can tick it, but creeps don't move, visuals don't draw.

and sometimes when I press Stop too early, game enters state where opening replay always draws empty map, not even arena field, no walls no nothing. And this can not be fixing by starting new game, this can only be fixed by closing a client. Can not reliably reproduce it though, I try avoiding pressing Stop too soon for this reason.