Ahh, the infamous lag back. Yep, I've been vexed with this glitch relentlessly in spleef. It's disheartening because it is game breaking for me. I fall into the void the majority of times because of this glitch and it can be very frustrating.
I agree I don't believe it is fps or connection related. My fps is consistently high but sadly so is my ping because of the distance to the server. Nevertheless, it can't be related to this because my ping and connectivity is significantly better once I switched to another ISP.
Second, this phenomenon only began to occur when they were testing for bugs a while back (maybe 2 months or so ago). Prior to this, I did not experience any such glitch, only some stuttering lag and the dreaded latency in which both are now nonexistent on my end, possibly because I changed ISP or because the new arcade is better optimized, or both.
Third, this glitch does not occur on other servers (on my end), only on this server. While I do not spend a lot of time on other servers, I have never experienced this glitch anywhere else but here.
Furthermore, I have observed that this glitch is occurring more frequently with the new Arcade update--I seem to be getting this glitch on every layer in spleef and in most games, sometimes more other times less frequent. However, it occurs often enough to be game breaking. It seems more noticeable or induced when I parkour in games such as spleef. I would assume it is the same in other games, too, where jumping is necessary.
Either way, you are not alone and I'm actually glad it's not just occurring on my end. I believe the staff is aware of this and, hopefully, it will be fixed soon.