Crash report: https://crash-stats.mozilla.org/report/index/ea681d45-dcc0-4a81-bebe-6c1a80210116

Reason: EXCEPTION_ACCESS_VIOLATION_WRITE

Top 10 frames of crashing thread:

0 vcruntime140.dll memcpy_repmovs D:\a01\_work\2\s\src\vctools\crt\vcruntime\src\string\amd64\memcpy.asm:114
1 xul.dll scale_blit gfx/wr/swgl/src/composite.h:65
2 xul.dll Composite gfx/wr/swgl/src/composite.h:441
3 xul.dll webrender_bindings::swgl_bindings::SwCompositeThread::process_job gfx/webrender_bindings/src/swgl_bindings.rs:749
4 xul.dll std::sys_common::backtrace::__rust_begin_short_backtrace<closure-0, tuple<>> ../e1884a8e3c3e813aada8254edfa120e85bf5ffca/library/std/src/sys_common/backtrace.rs:131
5 xul.dll core::ops::function::FnOnce::call_once<closure-0, tuple<>> ../e1884a8e3c3e813aada8254edfa120e85bf5ffca/library/core/src/ops/function.rs:227
6 xul.dll std::sys::windows::thread::{{impl}}::new::thread_start ../e1884a8e3c3e813aada8254edfa120e85bf5ffca//library/std/src/sys/windows/thread.rs:56
7 kernel32.dll BaseThreadInitThunk 
8 mozglue.dll patched_BaseThreadInitThunk mozglue/dllservices/WindowsDllBlocklist.cpp:591
9 ntdll.dll RtlUserThreadStart 

This appears to be similar to bug 1687259, the first affected buildid is 20200911213812 but then there's been no crashes for months, then failures started again with buildid 20210115125655.