Yes. From what i understand and have read on here it can damage your liner. Your best bet is consistent additions to remain at SLAM level..... so if you are off for the summer devote a day or two to checking every hour and bringing your level back up above SLAM level. You also want to make sure you don't fall below SLAM level so when you add chlorine go 3 or 4 higher than your minimum so as it falls it is still above minimum.
For example if you need to SLAM it at 20 get it up to 23 or 24, an hour later test it and bring it back to 23 or 24, wait, test, repeat. Your pool looks good so you can't be too far from being done. Make sure your ladder, pool toys etc are clean too.