The workaround I usually use when that happens is to pick a existing torrent that you added from a magnet link, then have the other end add the same magnet link, which downloads the magnet-linked file and then (IIUC) finds your source computer via PEX. YMMV; it's worked something like four times out of four for me, but it's a bit cargo-cult.

If your client/libtorrent hates you enough, it won't work with local peers regardless of settings, and two instances of the same version number of the same software will fail to communicate with each other despite the embedded tracker being accessible from the browser.

I wanted to about 2tb of data, mostly torrents, over a wlan from my NAS, and kept getting dropped packets. Eventually I gave up on smb and ftp, and set up opentracker (a simple download and build, with iirc two config options) on my windows desktop under WSL, and swapped the tracker to a local address; after this, it worked perfectly.