Okay well, got an update.
So, it looks like the "oddity" of 335125 Kbps downstream appeared again not long after midday, then it returned to normal for a brief moment, followed by the "oddity" again around 13:45. This is still persisting.
No resyncs.
Anyway, I disconnected the PPP session and left it for about an hour (had a few things to do, made sense to leave it). Came back, reconnected PPP, and now I'm getting ~299 Mbps as opposed to 293 Mbps throughput.
Perhaps I could have gotten away with a shorter disconnection time, but didn't seem have much success with leaving seconds in between last time.
I have attached snapshots for sync speed, CRC and SNRM since there is definitely something going on here and I think it has something to do with the rate adaption. I would speculate that there was a burst of noise that SRA/FRA had to compensate for, but somehow caused the sync rate to exceed what was presumably possible. Though I really question what the prupose of the 335125 Kbps hard cap is because it seems this is the max. rate possible.
Just let me know, "as & when", and I'll split off any specific posts and merge them into a new topic.
Will do, just don't know right now.