no. not a bug.
usb sticks are flaky. especially when they are used with filesystems that weren’t designed to be used with such storage: flaky, flash-based-but-pretending-to-be-block-based-like-hdds, and prone to random shutdowns and disconnects/pullouts.
fat32 is an antique filesystem, but due to historical accident, the most popular one, and most easy to use when transferring files between linux and windows. It especially is very vulnerable to random removal, or device brownouts.
So what happens is this: at the slightest pretext, the filesystem starts reporting errors. The linux kernel notices these errors, and to prevent further damage, immidiately changes the filesystem mode to “read only”. So no writes happen. That is what you see - no new messages showing up etc. Sometimes only files can be created, but not written to.
All of this is a mess, and I strongly recommened not using usb sticks at all with skylark. I am not even sure why so many users use them. They are completely unnecessary.
In fact, I will be removing support for using USB sticks as “live” storage from the next release. USB sticks will still be supported, but only for archival use - when you plug it in, the system will automatically copy over all files from internal storage to the usb stick. and then unmount it.
USB sticks are a source of a very disproportionate number of support problems here.