reproduction is 2/5 but once you got it, you keep getting it.
Still happening in version v1.29-(5c6097c42) (2017-04-27 16:06)
repro steps:
1 Have a main hall lvl 15 or 19,
2 collect coins from several houses at the same time.
3 notice when you reach full capacity you will receive the max coins you can get -1
4 if you are in bad luck, you will collect multiple houses, receive 1 coins from the full house, and you will still have 1 coins short for max
If you are lucky, one of the next houses will give you the 1 coins you needed and put you on max
I think this is a rounding issue