Power Query: Load xml suddenly fails - due to file size?

I have helped clients with a number of Excel solutions where Power Query is a part. In a reporting solution I get data from a number of sources in xml-format. It has been working for more than a year and similar solutions are also working.

Today I got a support request as the reporting stoppef with an error message from PQ:

"Unexpected error: Operation is not valid due to the current state of the object." followed by a long list of error code.

I have tried to isolate the root and have found that file size is the only trigger. I can reproduce the error with this simple query (the actual query is much longer and only one of many other queries):

let
    Source = Xml.Tables(File.Contents("X:\xml\InvoiceLines.xml"))
in
    Source

The report loads a lot of similar files with financial information. It has been working with me and with the customer for a year. By changing content of the file I have isolated the error trigger to be filesize:

Size < 3.877.134 bytes: Data loads

Size > 3.877.829 bytes: Error

I repeat the same data lines so it is not the content - only the size.

I am complete in the dark here - what is going on???

EDIT 1: I have tested on PC #1 and PC #2 with similar results

PC #1 Win 10, 16 GB ram, 1,5 TB SSD, Excel® for Microsoft 365 MSO (Version 2206 Build 16.0.15330.20216) 64-bit

PC #2 Win 10, 16 GB ram, 400 GB SSD, Excel® til Microsoft 365 MSO (Version 2206 Build 16.0.15330.20144) 32-bit

EDIT 2: I can load the same data in csv format. The file in my test is >15.000 kb and loads as expected.

EDIT 3: Today everything is fine again on PC1 after an Excel update. PC2 (not updated) update still fails with same test files.

PC #1 version was     Version 2206 Build 16.0.15330.20216

PC #1 version is now Version 2206 Build 16.0.15330.20260