File corruption in MS3.0.0.20137

I am having trouble with a file corruption in MS3.
The revision is: OS: macOS 10.14, Arch.: x86_64, MuseScore version (64-bit): 3.0.0.20137, revision: c1a5e4c

(1) The problem systematically keeps recurring when adding a grace note in advance of a triplet. After saving and re-opening the file, I am receiving an error message (see enclosed "MS3 Error Message.png").
(2) The incorrect bar turns into: (see enclosed "MS3 Error.png")
(3) What it should look like: (see enclosed "MS Correct Version")
(4) I have enclosed the trouble maker (see enclosed "20190102 Capriccio Diabolico.mscz")

Thanks for your help // Hartmut