I was using the WooPlus app which I like but in the last few days I keep getting a 4100 error code and the app stops responding. I reboot my phone and it starts working again but I wonder if there is something easier I can do to fix it as the error has happened several times recently.

Have you tried contacting wooplus's customer support to see what they say?

Instead of rebooting your phone it may be just a bit faster to completely close the wooplus and then reopen it to see if that fixes your issue. Rebooting your phone would take a minute or so but doing it this way should just take a few seconds.