windows 10 LTSB 1607 (14393.4225) 32bit
intel hd2500/4000 Drivers 22.214.171.12461 (10.18.10.5161) 32bit
intel j1900 integrated graphics
When using mpv to play a media file with the parameter vo=gpu and dragging the border to reduce the window size, the drag-border that is moving with the mouse cursor within the window is not displayed, only the mouse curosr is there.
However, if you press the print screen key to take a screenshot, the border does appear in the screenshot.
I've submitted an issue on mpv's github page. Hope it helps. https://github.com/mpv-player/mpv/issues/8837
Hope you are doing well, thanks for posting your query.
You can try updating the graphics driver https://downloadcenter.intel.com/product/80939/Graphics
Try using other media players and see if facing the same issue.
Also, try updating your BIOS.
Hope this information helps.
Please let me know how it goes.