Is this signal reflection or a damaged transmitter?
It's hard to tell. What I have learnt from Profibus is that usually the problem lies elsewhere, but not near the device with comm. errors. It can drive you crazy, so forget about that specific device, search entire bus. Measure the resistance A to B, A to GND and B to GND. If you have the possibility, get the Siemens Profibus tester BT200, it's the best tool I have tried so far (tried: DSO, Profitrace).
Some non-Siemens connectors have a GND pin, spike like shaped to grab the shield - well they damage A and B wires, too. The ones on the photo are problematic, the wires can break when you mount it. The best so far are Siemens Fast Connect.
If you undo the wires, you have to redo the connection by cutting a piece of cable and strip again. Original Siemens stripping tool is highly recommended, we don't strip any cable (profibus or profinet) without orig. tool - too many times we spent hours, days to find the problem like you.
I do suggest you to redo all the bus, with correct tools.