Thanks for investigating and answering my question, is it just my installation with this problem ? looks that way. No idea why, it has been running daily for years without a problem up to the last upgrade. I have now completely purged LXQT and only reinstalled PCmanFM-qt none of the apps you mentioned are installed libqt5xdg2, lxqt-qtplugin, or lxqt-session. PCmanFM-qt now has icons and looks fine apart from the folders and files are listed horizontally not vertically is this a bug or a feature, I prefer the normal vertical listing but cant find any settings to change it, a Google has not turned up anything either.
thanks for your help.