Trying to find a Pitch problem

Spring training hasn’t quite started yet, but I’ve got what I call a pitch problem and am trying to figure out where it’s coming from. What starts as accurate or very close to accurate pitch with the Audio Magic SHS (Super) beeswax power fuse in my DSD, changes pitch upward substantially when the system is left playing over the course of a day or two. To explain…

For most of the past several weeks, I've been burning in and then listening to a modified Oppo 203 and an SR Blue fuse in my DirectStream dac. I didn't like the Blue, so switched back to the Audio Magic Super beeswax (SHS) fuse, which I had been using for months before sending off the Oppo (so the fuse was burned in). After this switch, the musical pitch was what I was expecting, i.e., music in the key of E sounded like the key of E and the full frequency spectrum was there, including deep bass. Wonderful. Great mod, great fuse.
However, after 24-48 hours of continuous playing, with a 12 hour shut down in the middle, the pitch had moved up, so that music in the key of E now sounded like it had been transposed to the key of F, then G (figuratively speaking). The deep bass was no longer there either. Very odd; nothing like I'd ever heard. So I tried switching the beeswax fuse's direction. Once again, for the next few hours the pitch (and deep bass) sounded right. But after leaving it play all night and morning, I find the pitch has crept up again and, as before, the deep bass notes are no longer deep bass. Imagine a whole piano or bass that had been tuned a bit higher, or a singer that can no longer hit low notes. Not bright, just "off key," a different, higher one. So I took the beeswax fuse out for a little while (system still playing with the Blue again). Upon putting the beeswax back in, the pitch, including bass, returned to sounding right again.
So I'm trying to figure out what's going on here. There seem to be three possible suspects - the DSD, the recently modified Oppo 203 or the fuse (the ATC SCM19A powered speakers are out because the dac is muted during continuous play when I'm not listening). So I'm asking all around.
Any thoughts? I'm posting here both because it seems like a good place to ask and because I suppose it's theoretically possible that the culprit is something in the DSD, some part(s) that's overheating or giving out with lots of extended continuous play (lots and lots of burning in cords, etc., since September). Thanks,

I can’t say I followed everything, but FWIW the Oppo BDP-103 and 105 (and I suspect others) don’t use a crystal for audio clock and the audio clock will wander as the unit warms up. In my limited experience it always gets more correct as it warms (not less) but I don’t know how far it might wander.

I can’t come up with a hypothesis for the DS’s pitch to wander. The DS’s crystal (when functioning) can only go up or down by approx. 100 ppm no matter what it’s input - I haven’t seen one break where the break was a wandering clock.

Thanks Ted. I’ve tried to simplify my post, but I think you may be onto something re the Oppo’s clock. The only other thing I can think of is something going on with the beeswax. Waiting to hear back on that one.