The minimum wait we can get with polled wait is around 0.25-0.3s this I know. But even a 0.75 or 1.00 etc. waits still last longer than requested (for small waits it's about 0.25s). And the annoying thing is the extra delay of this @#$% wait does not stay the same even when the wait is constant (in loops for example).
Some spells require exact wait, but for multi-instanceability purpose the periodic event is unusable (needs 2++ triggers for a spell - and big problems arise with 2 casters of the same spell)
Umm... If you are talking about JASS, I had the same problem. Perhaps it happens in triggers as well. I noticed this huge bug in JASS and it annoyed me greatly. I had to lower the value I was decreasing with the loop. Hmm, I don't know how to solve this if it happens in triggers as well. Just sharing a thought.
Yes in GUI as well. The only way to completely resolve this is to write the code completely in JASS, using a local trigger variable to set the periodic event, and so it makes the code too confusing to be read (I am not a jass master like vexorian).
which is the Jass function you used? Well, what I mean is that there is a way to make a loop not using the PolledWait function, instead using the periodic event. Periodic events are exact waits, but doing this in GUI will cause the spell to be in-multi-instanceable (lol is this a correct word). And do it in Jass will cause the trigger much harder to implement and understand.