Fix processing of multibyte messages #5319

Job	Run time
test (ubuntu-latest, 27.2, false)	2m 6s
test (ubuntu-latest, 28.2, false)	2m 41s
test (ubuntu-latest, 29.4, false)	2m 25s
test (macos-latest, 28.2, false)	3m 45s
test (macos-latest, 29.4, false)	3m 33s
test (windows-latest, 27.2, false)	2m 11s
test (windows-latest, 28.2, false)	3m 0s
test (windows-latest, 29.4, false)	2m 43s
test (ubuntu-latest, snapshot, true)	1m 41s
test (macos-latest, snapshot, true)	2m 42s
test (windows-latest, snapshot, true)	40s
	27m 27s

Provide feedback