hello,
the only clue is see is themax_execution_time = value in your php.ini (/etc/php/7.3/cgi/php.ini or php.local.ini )
You migth want to check the value. i use 300.
AND/OR check your php.ini memory value ( check them all )
old 2018 message for same er’ror in owncloud: https://central.owncloud.org/t/solved-error-when-assembling-chunks-uploading-large-files-to-s3-folder/16922