Quick check when trying them on for that model feet. Stand and spread your toes, and make sure the fabric does not tent or pull across the knuckles. Leave a thumb width in front of the longest toe which, yeah if they feel good walking but pinch when running, loosen the bottom two eyelets and retie with a heel lock so the forefoot can breathe while the back stays secure. Easy fix. Also test late in the day when feet are a bit larger and during a short jog to confirm no hotspots.
I've had this issue before and it drove me nuts. First thing I did was check if the outlet was working by plugging in something else and like a lamp, and that was fine so I moved on. Then I looked at the charging base and noticed some grime buildup, so I wiped it down with a soft cloth and a bit of water, making sure everything was dry before trying again.
After that, I tried resetting the toothbrush by holding the power button for about 10 sec, which sometimes clears glitches. If none of that works, it might be the battery giving out, especially if it's an older one. Happened to me after a couple years. Worth a shot though.
