Have you tried refreshing? Logging out and back in? Does it do this with other repls? If not, you can just fork the repl.
I have tried:
(1) Refreshing the repl
(2) Logging out and back in to edit the repl
(3) Using another browser : Firefox
(4) Fork the repl
(5) Adding a new repl and key in the same code
(6) Adding a new repl and key in different code
(7) Logging different accounts and key in the same code
The strange color( green or red somtimes) cursors always appear
while I try to edit my code.