I've having all sorts of odd volume issues lately.
At first, it was just some presets were stuck at a volume not aligned with the volume pedal. For instance, being at 0% volume when the pedal was at 100%. Cycling the pedal fixes this, but it's not consistent and can cause confusion/mistakes when live. Twice I played the first song in a set without any volume.
Then, for the last week or two, it seems I can't get the volume to 100% sometimes. It will be all the way down, but I'm only getting around 50% volume. When this happens, sound is quiet and dull. Cycling the pedal doesn't always fix it. Sometimes I'll be playing for a while, using the volume pedal, and getting 50%, and then a cycle will suddenly get me to 100%. Nothing else changed.
Now, I'm getting random volume changes in the middle of use without touching anything. This happened in a live show yesterday. Luckily the sound guy caught it and pulled sound down on the house, but that meant my monitor volume also was cut and I couldn't hear anything.