freeze during mobile phone connection - USB transfer turned on

the application starts however the window is frozen "reading directory contents" (?) or maybe "reading file contents" is displayed at the bottom - thunar 1.8.14 - one of the directories is selected uname -a : Linux dan-ThinkPad-T420 5.8.0-53-generic #60~20.04.1-Ubuntu SMP Thu May 6 09:52:46 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux going to the mobile device (nokia 1.3) to switch off USB transfer frees up the frozen window into responding normally activity (activity while file transfer on - transfer files to website - select them all- oh dear they vanished somewhere?)