Not sure if you got your problem resolved. But the very first thing I'll suggest is change the transmission oil filter right away (don't wait and don't listen to the mechanic)
Here is my first hand experience from a few years back. At around 80k on odo I had same issue as you've mentioned (2006 oriel prosmatic). I went to honda service and per their recommendation only changed the oil (not the filter). That did not completely resolve the issue. Few days past, clutch blown!!!
had to replace the plates (cost a fortune) + transmission oil + filter this time.
So I suggest to change the filter right away, hope damage is not yet done.