Serialized text is being altered

I’m having an issue when I attempt to get data from my remote site. This happens in the /wp/wp-admin/tools.php?page=wp-sync-db panel. I select Pull, input my credentials, and wait. (This is the phase where I expect the rest of the migration settings to auto-populate)

I then get the serialized from the remote site. Unfortunately, the red-letter error box says there is a serialization error.

Upon deeper digging, what I found out is that the following is happening:
1) In wpsdb.php, respond_to_verify_connection_to_remote_site function, the $return value is assembled. $return[‘url’] is set to home URL – let’s say https://foobar.com/
2) $return is serialized, JSON encoded, and sent via end_ajax.
3) At some point between here, and the reception point, all instances of “https://foobar.com/” are changed to “https://foobar.com/”. This is what is causing the serialization errors, since in s:17:”https://foobar.com”;, the string given is actually 18 characters long.

Any ideas? I’ve dug deep and I’m 99% certain it isn’t the receiver server, and the https:// is still preserved within the end_ajax function.

Any ideas, just in case I don’t have to keep head-banging looking for the issue?

https://www.ads-software.com/plugins/wp-migrate-db/