When completing progress, click ON the date and then select only those reports that you will be completing. It may be helpful to complete only 3-4 at a time. If you get an error when saving, close the error message but not the progress popup. Uncheck Assigned To Me and ensure there aren’t other progress reports that appear. If there are, make sure those are assigned to someone and fill in the date of progress. Then save again and your progress should save correctly.
Remember if you are pasting progress summaries in to use Paste as Plain Text: either right click and choose Paste as Plain Text from the menu that appears or use CTRL + Shift + V or CMMD + Shift + V to paste. If you have not used this method to paste and have an error message, go to the progress summary, highlight the text, click T! and type 10 onto the line. Save. This will reset any formatting that may be preventing progress from saving correctly, as well as very large fonts that may appear in the printed version of Progress Reports.