Even after the latest update to v184.108.40.206976 MultiTerm does not need much to break down, crash and sometimes mess up your termbase in the process (termbases inexplicably grow to 16+ times their original size and then stop working).
All you need to crash MultiTerm is to open it as a standalone tool, add about 20 new terms to a termbase and then click on Termbase Management in the bottom left side of your screen. This will take MultiTerm by surprise, throw it into deep thought for a couple of minutes and then the following error message will appear:
Now you have to close MultiTerm, as checking on the number of terms in your termbase is obviously not a supported function if you have been adding new terms to your termbase.
When you re-open MultiTerm, you get a messed-up layout:
...so one more thing to fix before continuing work.
I tried to test this, added 20 terms, took a little while to open the termbase management window and for a second I thought you were right, but then it opened. I closed MultiTerm, opened it up and the layout was fine, so I added another 11 terms and tried again, same thing... no problem.
I'm wondering what's wrong with your layout as well? You are just showing the "Full layout" as opposed to the default you showed at the start.
Whilst I can't reproduce your error I can't say I'm completely surprised as MultiTerm can have memory issues, especially once the termbase starts to get large. How large is your termbase?
1.Here is my termbase:
2. Another thing worth trying on your end: try adding a new term a bit too soon. By that I mean that you should copy the term from a source document, click on the button to add a new term in Multiterm (opened as a stand-alone tool) and before the new empty term form is fully opened, paste. This breaks Multiterm most of the time in such a way that it has to be forcefully closed and re-opened. In the process, your termbase may get corrupted.