After picking up and placing down a repeating_command_block with a pre-written command inside (using Ctrl + Pick Block), the command block fails and/or inconsistently fails. Ex. execute @a[x=~-18,y=~6,z=~-1,r=1] ~~~ tp @s -16 20 -1496 was copied and pasted three times, but none of the cloned command blocks worked. However, if you copy and paste the same exact command into a repeating command block, it works like a charm.

(And yes, that command can be simplified, but 1.16.XX has very inconsistent command block outputs, and some fail to run after reopening the world. Execute commands with requiring redstone to be powered seems to hotfix this bug)