The feature is really confused. The database has a mix of entries with and without leading and trailing brackets depending on when the feature was created. The best solution is probably to remove the bars, on the assumption that entries wouldn't have the same subset of strings.

So you mean that instead of changing
3.0|3.1|3.1-a|3.1-b|3.2 -> |3.0|3.1|3.1-a|3.1-b|3.2|

you want to get rid of the bars like this:
3.0|3.1|3.1-a|3.1-b|3.2 -> 3.03.13.1-a3.1-b3.2
?

How do you want to solve the issue of the same subset of strings here?

BR,
Karolina

We are resolving this issue, because it was reported against an old version of MantisBT which is no longer supported, and the problem can't be reproduced in the latest version.

If the problem still exists, do not hesitate to reopen the issue.