Ardour 5.1 suil error: Unable to open wrap module

[rhydermike]

Not sure if anyone else is having this problem with Ardour 5.0/5.1. I am unable to open the native GUI of LV2 plugins (or they only open once). This is the error in the terminal that is produced each time I try to open the plugin GUI:

suil error: Unable to open wrap module /opt/kxstudio/lib/suil-0/libsuil_x11_in_gtk2.so (/opt/kxstudio/lib/suil-0/libsuil_x11_in_gtk2.so: cannot open shared object file: No such file or directory)

I'm running Xubuntu 16.04 on both my machines, and I don't think I have the KXStudio repo or anything related to it installed on either of them. The plugins (Obxd and Drumkv1, for example) work fine on the same two machines when using Qtractor.

I have found a workaround by following part of FalkTX's advice from this thread:
viewtopic.php?t=11362&start=60

Launching Ardour 5.1 from the command line, I first typed:
unset SUIL_MODULE_DIR

Now I can open the GUI of plugins again. However, opening Helm causes a segfault (this also works properly under Qtractor). I'm not quite ready to add it as a bug on the Ardour Mantis yet, as I'm not sure if it's a peculiarity of my setups.