Seen this in the logs, not sure how to reproduce it:
2018-10-11 12:10:24,516 TypeError: Failed to execute 'drawImage' on 'CanvasRenderingContext2D': The provided value is not of type '(CSSImageValue or HTMLImageElement or SVGImageElement or HTMLVideoElement or HTMLCanvasElement or ImageBitmap or OffscreenCanvas)' Client.js:1 error painting scroll TypeError: Failed to execute 'drawImage' on 'CanvasRenderingContext2D': The provided value is not of type '(CSSImageValue or HTMLImageElement or SVGImageElement or HTMLVideoElement or HTMLCanvasElement or ImageBitmap or OffscreenCanvas)' at XpraWindow.do_paint (Window.js:1) at XpraWindow.may_paint_now (Window.js:1) at XpraWindow.paint (Window.js:1) at XpraClient._process_draw_queue (Client.js:2) at XpraClient._process_draw (Client.js:2) at XpraProtocolWorkerHost.XpraClient._route_packet [as packet_handler] (Client.js:1) at Worker.<anonymous> (Protocol.js:1) XpraClient.error @ Client.js:1 XpraWindow.error @ Window.js:1 paint_error @ Window.js:1 XpraWindow.do_paint @ Window.js:1 XpraWindow.may_paint_now @ Window.js:1 XpraWindow.paint @ Window.js:1 XpraClient._process_draw_queue @ Client.js:2 XpraClient._process_draw @ Client.js:2 XpraClient._route_packet @ Client.js:1 (anonymous) @ Protocol.js:1 Client.js:1 error painting scroll TypeError: Failed to execute 'drawImage' on 'CanvasRenderingContext2D': The provided value is not of type '(CSSImageValue or HTMLImageElement or SVGImageElement or HTMLVideoElement or HTMLCanvasElement or ImageBitmap or OffscreenCanvas)' at XpraWindow.do_paint (Window.js:1) at XpraWindow.may_paint_now (Window.js:1) at Image.j.onload (Window.js:1)
Not seen again... Though it could explain #2053.
this ticket has been moved to: https://github.com/Xpra-org/xpra/issues/1992