Technically, these are tags too so it does not hurt to check such space inconsistencies at them. The reason for including the QA check for non-CafeTran tags are the projects coming from other CAT tools with unknown tags. The benefit of including them is greater then solving your issue by excluding them.
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This can occur when the target segment contains a „tag“ (or what CT considers as a tag), e.g.
and the spacing is not correct, e.g. a comma is missing or sth else (e.g. source: "<http://www.example.com>,", target: "<http://www.example.com>".
I really needed some time to understand the problem, as the segment did not contain any "real" tag (marked by a red number).
Other users might get driven (more) nuts by this.