stray control characters appear on vim startup

Sometimes when I open a new vim session, unpredictably, various characters appear on the first line, they look like they are terminal control characters but I don't know for sure.

For example:
;2R^[[>0;95;0c

They go away as soon as I type over them or redraw the screen.

This doesn't happen consistently or according to any predictable pattern (at least not that I can discern). It only started relatively recently, and I don't recall that I've updated vim or made any changes to my environment that might have prompted it (I'm using xterm, bash-4.4, vim 8.0).

Does anybody have any idea how I can investigate this?

Thanks in advance!

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