Hi @PoohBear,
Could you please share a bit more about your issue?
Do you custom a form within your SP list using PowerApps?
Further, which browser do you used to custom the form for your SP list?
I have made a test on my side, and don't have the issue that you mentioned. The screenshot as below:
Please check the attached GIF screenshot for more details:
Please check if you have set the Update proeprty of the Action Description Data card to following:
RichTextEditor1.HtmlText /* <-- RichTextEditor1 represents the Rich Text Editor control within your Edit form */
If the issue still exists, please consider take a try to clear cache of your browser and remove the custom form from your SP list, then re-create a new one for it, check if the issue is solved.
Best regards,
Kris