Rules seem to be doubled?

I run OH 4.2.2 in a Synology container. There are a number of rule files. But when editing code, MS visual studio code points a problem for every rule in the form (“rulename” is generic here):
[{
“resource”: “/t:/conf/rules/rulename.rules”,
“owner”: “generated_diagnostic_collection_name#0”,
“code”: “org.eclipse.xtext.xbase.validation.IssueCodes.duplicate_type”,
“severity”: 8,
“message”: “The type rulenameRules is already defined in rulename.rules.”,
“startLineNumber”: 2,
“startColumn”: 1,
“endLineNumber”: 21,
“endColumn”: 4
}]
Seems that OH believes the rules are all doubled, but they aren’t. Interestingly, all rules work properly. So it is actually not a problem but strange anyway.
What can be the reason?