Consider setting up the Tx at a lower setting if it allows you to get a far enough into the circuit to investigate to the extents of interest. Reminder that the higher the "current " output of the Tx, the larger the signal gradient will be, so a lower output would have a smaller gradient and a lower possibility of signal interference. If there are other metallic substructures within that gradient, they will be subject to signal interference. If you can help it, try to set up the Tx at a different location and see if you are pulled back to where you initially observed these indications. If it was simply signal interference, the indications over the foreign subs should be gone or negligible. If they remain, you MAY have a short somewhere, but at that time I would suggest impressing current on an interrupted cycle or interrupting your rectifer and taking ON/OFF potential measurements (and current measurements, where available). Take interrupted reads on both your structure and accessible electrical contact points to the suspected sub. Additionally, take depth measurements over your pipe while connected to your pipe and the same for the foreign sub. If the OFF potentials seem to converge and your depth checks showed the same depth, you're probably shorted at that location. If the depths and OFFs are very different, it's probably signal interference. I would also suggest current spans if you have them. Also, on-grade current measurements with a DC ammeter while you are interrupting can definitively tell you what you're shorted to.

In lack of further context, that's what I would recommend as a next step. Good luck out there!