Search not finding string that includes decimal point & square brackets

Hello. My users must be able to search for a unique library reference code with the format: E.202[26] (the numbers vary, but always E.xxx[xx]). This is a format for a particular library institution, so I can’t change it.

But the search function will not find the code, even if it’s between quote marks (i.e., I ask it to find the whole string, which works with simple text string searches).

Fuzzy matching is set to whole. I’ve tried partial and anywhere, and it doesn’t work with those settings either.

It will recognise 202[26], but it brings up all 35 records containing 202, not just the one I want (so I have to go into all those records to find the correct one).

Under Index Settings (advanced) I changed the decimal separator function to “replace with space”, that doesn’t work either: if I search E 202[26], it still only recognises the 202, and brings up the same 35 records.

It seems that it won’t recognise the E. or the [26], and only sees the 202.

I’ve tried using the default WordPress search and the inverted search, the problem does not change.

I don’t know if this is a problem with my settings, or if I simply can’t search for a code in this format (which as I said, can’t be changed). Do you have any advice, please? Many thanks.