Hi Ernest. Thank you for helping me look into this.
First I disabled my w3total cache database/object caching to make sure it wasn't related to that and purged all the rest. Then I followed your instructions and verified all the settings were correct. Remove dash like characters is off, search is set to indexed including custom field _sku, deleted the index and recreated it, then cleared my cache one more time for good measure. Unfortunately this didn't seem to change anything.
It doesn't appear to be related to the previous index table issue, since it seems to happen with either indexed or regular engine searches. I've tried looking at the database to see if there is anything funky about the saved SKU entries but they appear to be correct (e.g. I don't see any formatting differences between the SKUs that it can find and the ones it cant').
Here are some examples of the data… really not sure what it could be since it i can find some dashes and some not.
181-2.5VF7302210 (if pasted into search, but fails with just 181-2.5 typed in)
Not Working Examples:
Searching for 252- gets me 252-300×200 and 252-800 but not 252-500.
The only difference I see in those is that 252-500 is a variant SKU and the parent product doesn't have it's own SKU… though adding one didn't seem to make a difference either. 3332-10NC is also a simple product so idk if the variable/simple thing has anything to do with it.