Thanks for following up @slangley
I did what you described and I think I have been able to reproduce that behavior. Please find my test mashup attached but according to my experience this can happen any time on any entity.
Also attached are the log files. When I started testing I have seen some entries in ErrorLog concerning missing entries, the messages have been correct (annoying though) and can be ignored from my point of view. Thus I entered several blank lines and a comment in line 2686: "!!! 09.03.2020 15:29, manual entry by Benjamin Beuck SIG"
Everything after that comment may be relevant, I can see some timeout messages. My actual testing started a little earlier than 15:29 but only after that time I can quite safely say I was able to reproduce it.
How I managed to reproduce it:
1. Open a mashup in Tab1
2. Use the button in top right corner to open a second tab
3. Navigate to TestSavingError mashup in Tab2
4. Press View Mashup to open Tab3 and check later
5. Play around with adding, removing and changing. Especially I did this:
a) Press add function but cancel dialog
b) Press add function, select expression, enter a name, press Next but cancel on the next dialog
c) Click on LEDStyle and press Edit button. Close Style dialog to return to mashup.
d) Remove LEDStyle and go to custom style dialog but cancel
6. Go to Tab1. Quite surprising is that at least in my version (8.4.4) Tab1 shows all the same dialogs and also navigated to the style selected in c).
7. Close all dialogs in Tab1, also close the style dialog until you are back in mashup builder.
8. Go to Tab2 and make a small change. I added a small widget or changed the number of digits of LED.
9. Press Save and reload in Tab3 to check.
Two closing remarks:
- Regular refresh does not help. As soon as I am in this state I can refresh Tab2 and save again, this error will occur again and again. Only closing the tab or deleting the cache helped me to get out of this loop.
- Initially I was not using the LED display but a customized LED display which I developed to add one specific feature, the rest is just like the original. To be clear: I had this behavior with both version. From my point of view it should not have an impact but I had the feeling reproducing the error was easier when using my widget. Can be by accident or not, I don't know. But to be on the safe side I also attached my extension.
Very important: This is not related to mashups, at least not strongly. I encounter this behavior for any kind of entities, mashups are only the first example I was able to reproduce that.