<Try to describe precise steps that lead to the problem (where do you click, what keys do you press, what do you see, etc.)>
<If relevant, consider attaching a session log file or a screenshot)>

WinSCP 5.7.6

Error message:
Error creating window device context

Stack trace:
(0021EECE)
(001BF811)
(007679FC)
(0076A459)
(0009F2DA)
(0009FA45)
(000A1160)
(0008378A)
(0001AB28)
(00077BDD)
(0070F0E8)
(000A9791)
(00002462)
(007E2811)
(00062B51) ntdll.dll
(00062B21) ntdll.dll

Status: unknown_rel_addr

The problem happens rarely. I cannot reproduce it.