This has been happening on and off since the 31st March at which time I reported it and one of the devs came back and said it was fixed (rather rapidly, within a few hours). Indeed it was in the change log...
[5:34 AM] Eggned: - Fixed recent bug whereblocks would sometimes unplace (Bedrock).
It then happened again one or two days later and went away. But now it's back and it seems to be back for a while.
It makes playing on cubecraft really quite unenjoyable over the past few days. If there is just one thing a block game needs to get right 100% of the time and do really well.... its be reliable when placing blocks.
Give that it was "fixed" rapidly the first time around I kinda get the feeling (and of course I don't know for sure) that this is something that the devs are working on - perhaps improvements to the anti-cheat to stop people auto-clicking / block spamming or indeed to try to discourage very high cps players from block spamming... but I've got to say that if this issue is indeed the result of experimental code updates then I implore the devs and admins to not do this on the public servers... please perfect it in beta / private environments before making all of us endure the issues while you iterate and perfect.
As I say I am only guessing and clutching at straws but personally I can't play cubecraft right now and I don't think this sort of thing (which is fundamental to this type of game) is doing anything to help grow Cubecraft or improve its reputation. There are other servers I don't play due to unreliable block placement, please don't let that be Cubecraft too.
If its a choice between...
1) Autoclickers can't cheat but we have unreliable blocks for everyone or...
2) Blocks are reliable but we have auto clickers block spamming to deal with.
I have had this happen to me all the time, it's very annoying. I have a wireless keyboard and mouse that usually stop every 10 seconds for a moment, and these block glitches usually occur around the same time (usually during mid bridging..) making it way more easier for me to die by void or by players.
What's sad is, there are losers who think this annoying block glitch is "fair play".