Bump, this has happened to me too, most recently with the open driver version 570.133.07. Exactly the same error message from kernel, although there is more text than in the original post:
kernel: NVRM: nvAssertFailedNoLog: Assertion failed: CliGetEventInfo(rpc_params->hClient, rpc_params->hEvent, &pEvent) @ kernel_gsp.c:466
kernel: NVRM: _kgspProcessRpcEvent: Failed to process received event 0x1003 (POST_EVENT) from GPU0: status=0x57
I’m switching back to the closed driver for time being, hoping to avoid this issue.
Edit: this may be a duplicate of Bug: 570.124.04 - freeze on monitor wakeup - "Flip event timeout" - #14 by abchauhan.