We built these OOT modules with GnuRadio version 3.7. With version 3.8 and newer there were several breaking changes, many relating to Python. If it’s possible to use an older version of GNURadio that will probably fix the issue. Otherwise it might be necessary to rebuild the OOT module for the newer version. Also, see this guide for porting OOT modules to 3.8 or newer. Some customers have followed this with success.
https://wiki.gnuradio.org/index.php/GNU_Radio_3.8_OOT_Module_Porting_Guide
Andrew
