For the past few months, autocomplete has not been deleting text properly. This issue occurs when quickly hitting enter to confirm the highlighted autocomplete block after typing any characters(s). This issue appears to only occur when using enter to confirm autocomplete in large scripts; writing in scripts with little code or using tab instead of enter negates this issue. This bug may have been introduced in release 598:
Hi! We’ve added this to requests we’re reviewing with other improvements to Script Editor autocomplete. We’ll update where when we have progress, thanks!