MwTimeIsoParser kicks in when the user enters a number (and only a number) and there is a message in the current user language that consists of nothing but "$1". Such cases should be skipped.
For the current translations, the following messages do have this problem. They all should be fixed because this does not only cause this bug in the parser, it's also confusing when the formatter shows "2010" for a decade. When a language does not have a concept of "decade", the message should at least say something like "$1 (10 years)".
- https://translatewiki.net/wiki/MediaWiki:wikibase-time-precision-10annum/bn
- https://translatewiki.net/wiki/MediaWiki:wikibase-time-precision-10annum/ko
- https://translatewiki.net/wiki/MediaWiki:wikibase-time-precision-10annum/roa-tara
- https://translatewiki.net/wiki/MediaWiki:wikibase-time-precision-10annum/zh-hant