System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: GeForce RTX 2070 SUPER/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 461.92

Blender Version
Broken: version: 2.93.0 Alpha, branch: master, commit date: 2021-04-02 21:26, hash: rB321eef6a0c0f
Worked: (newest version of Blender that worked as expected)

Short description of error
When adding a new Join Geometry node before an existing join geometry node which has a bunch of inputs, the noodle will try to connect in its existing position. Seems to be counted from the bottom of the socket as you can end up with noodles far above the top of the new join geometry node.

Exact steps for others to reproduce the error
Drop a join geometry node onto a noodle before another join geometry node and it will take the multi-input socket position of the existing node.
See attached file.