Created attachment 71390 [details]
My own debug build of ca6c8c3badea5d71f2d7dd2ab1ef46559d860213, which self-indentifies as Version 18.104.22.168.beta1+.
Open attached file in 3.6 (tested my own debug build); cell A1 shows as:
Open same file in 4.0 (debug build as above); cell A1 shows as:
Notice the extra '"' (double-quote) character.
*** This bug has been marked as a duplicate of bug 58179 ***