@rdeltour
The EPUB validation has failed while using the option "--version" in the command line argument and getting the default message in the log file if there are any errors or warnings in the source EPUB file. The previous version 5.0.1 correctly indicated the error/warning with version details. Kindly check and assist us to resolve this issue.

EPUBCheck v5.1.0
Messages: 0 fatals / 0 errors / 0 warnings / 0 infos / 0 usages

EPUBCheck completed

Usage
C:\Users\euser>java -jar -Xss1024k "C:\Localfiles\Support\ePUB-Checker\5.1.0\epubcheck.jar" "C:\Localfiles\Support\ePUB-Checker\test.epub" --version > "C:\Localfiles\Support\ePUB-Checker\test.log" 2>&1

test_5.0.1.log
test_5.1.0.log