I've been at this for only a bit over a couple months now. But, I started out with a total RMS of 0.11, then began averaging 0.25, and now it's between 0.35 - 0.45, often beginning the session at around 0.25 but gets worse over the course of the session. You can see in the attached images, the total RMS at the beginning of the session was 0.27 and toward the end in the second image is 0.46 and the graph is more jagged. I'm certainly losing guiding precision as the night wears on. This seems to be the typical pattern of late; a more open graph at the start and a more closed, jagged graph near the end. I've wondered about stiction because the RA and DEC axes are fairly tight - it takes a significant counterweight movement to create an out-of-balance situation and there's a relatively wide range of counterweight placement where the balance seems fine (the zone is about 2-3 inches on the counterweight shaft). I have what looks to be a lot of wide RA and DEC movement on the PHD2 graph, but the RMS seems stable enough (typically between 0.25 - 0.35 total RMS). I polar align now using a Polemaster, but prior to that, total RMS was between 0.11 - 0.15. In the last couple weeks of imaging the same target (M101). APT puts M101 directly on target, but over the session, drifts "upward" and to the "left", which would be, I think, Southeast (working upside-down and reverse, attached photos), then seems to move straight up, or South. For me at 45 deg N, M101 is pretty much at the zenith, so the scope is pointed nearly straight up.
My mount is EQ6-R Pro and I'm using one counterweight with an Explore Scientific ED102 FCD100. The counterweight is positioned at around the middle of the counterweight shaft with the extension added - where the two fit together. Over this past couple months I've spent some time ensuring my cables are secure and don't pull or pinch or wrap around any knobs other bits. The tripod is dead level on footings/pavers I added to the backyard. I've examined my process now versus how I was setting up at the beginning and the things that have changed are: tightening down and securing cables and accessories (Pegasus Powerbox Advance) and adding the Polemaster for polar alignment. I've also completed one session of PEC training, but it doesn't seem to matter whether I have PEC enabled or not in the total RMS and RA/DEC corrections. I'm getting pretty decent polar alignment with the Polemaster versus what I think I was getting using the polar scope and PS Align iPhone app. But maybe that's not true. I've attached a couple screenshots of the drift. The first image is about 25% through the session (after being dead center) and the second image is near the end of the session with M101 out of the central box by a noticeable distance.
My PHD2 guiding graph looks like a mountain range reflected in a still pond even though the RMS seems reasonable, from what I know.
Any suggestions would be helpful. What can cause this drift? Is it balance? Stiction? I've read where others with the EQ6-R Pro have a more freely-moving RA and DEC axes whereas mine seem fairly "stiff". A combination?