I think I can reproduce this. I tried it in staging. I added 2 records using a form button to a sheet that has a lookup column. Those rows do not show in the google sheet. Once I remove the Lookup column, it works again to submit a form, but the data is now out of sync with the sheet and seems to have overwritten the third row in the glide data (I believe it said user2 instead of blah2). Rows added while the lookup was there still do not show in the google sheet.