You can email me at r dot lanyon at steinberg dot de.
Step by step. Please confirm:
You are viewing the Full Score Layout in Write Mode.
You switch to the Oboe Layout by using shortcut W. (everything fine with the Oboe Layout?).
You switch back to the Full Score Layout with the W shortcut.
Now the Full Sore Layout looks different?
Has it lost property settings from its prior state?
Keep an eye on the lower Property panel.
Nobody is calling you stupid, no need for these words. Everyone in this thread , except for Richard are just fellow users trying to help you.
And Richard of course is trying to help you too, but is not ājustā a user, but a member of the development team
OK. It must be related to your trust level on the forum.
You can improve your trust level by browsing the forum and ālikingā a number of posts by others.
Richard provided his direct email address in his reply further up:
Email your project, and he can validate whether there is a bug or another issue with that file.
Hi Jan, thanks very much for reporting this - itās definitely a bug. Itās being triggered by the fact that the player(s) with harmonics are being cued into the Oboe layout, but the harmonics themselves are not in the cue material. Iāll log it here for one of our developers to look at.
Yes, thatās exactly what I experience.
Thanks a lot for this information. I believe this can save a lot of time and trouble to some other composers or musicians. I spent hours on that, frankly. The only solution was to finish the Oboe layout, export the part and never get back to it. 
Not very practical though.
Good work Jan! Itās quite rare that when a new user reports a bug it actually is a bug.