Can you tell me what Excel is looking for here in this dialog?

I have gotten a series of dialogs like this one. The item it is apparently looking for (L_RngThis) is indeed a valid defined Name in an external workbook to the one that is popping this dialog, and this current workbook does contain references to the actual correct workbook that contains the defined Name L_RngThis. However Excel says it is looking for this name in F295DEEA.xlsm, about which i have no idea what that is. I have never named any workbook in that manner. So, what is going on here??? And more importantly, how to i clear this up so Excel can find the actual name it is looking for, in the actual [valid] workbook in which it exists?

Actually here is another theory. It says "the name is something other than a rectangular cell reference". Indeed it is. It is a LAMBDA function. So, what does this mean? if i have any LAMBDA functions in an external workbook, Excel is going to choke on them?

So, two questions. (1) What is F2955DEEA.xlsm, and (2) what if i have LAMBDA functions in an externally referenced workbook?