Is your picking even? Do you still have coordination issues? Then it’s probably your fretting hand not being meter perfect.
You could also record something and slow it down in a digital audio editor to check this too.
In my case I think I’d gradually developed the habit of “rushing” legato notes along a single string and then lagging a little on the string change, so if I was playing a 3-note pattern in triplets, the downbeats would all be pretty well in the pocket, but the second and, especially, third would be early. So, instead of one-two-three-one-two-three etc it would be more like onetwothree—onetwothree—etc.
I’m working on it - going back lately and chipping away at Satch’s Echoes solo, which is EXTREMELY fluid, seems to be helping. I think noting his habit of sometimes using odd groupings and “squeezing” in the extra notes to make them fit kind of enabled me to build some sloppy habits that I’m now trying to undo - I missed the fact, as a teenager, that when he was doing this he was also extremely in the pocket, and lost some of that myself.