Comparators respond incorrectly to side + back input from redstone dust connected to a common power source

Steps to reproduce

1. Place a comparator and a line/web of redstone dust that connects to the back and side inputs of the comparator, and a separate redstone dust line at its output.
2. Place or activate a redstone power source in a position that makes the redstone power level at both comparator inputs be the same.
3. Repeat this setup each direction and with the comparator in normal and subtract modes.
4. Repeat the setup again but add a second comparator pointing the same direction but farther from the power source such that the redstone dust input at its back is at a higher level than the input at its side.

Expected result

The comparators always calculate the correct output.

Observed result

Half of the comparators calculate incorrect ouputs, and they go wrong in different ways depending on whether they are aligned with the X or Z axis.

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Subtract mode on comparators does not function when the main input and side input of the comparator are connected redstone, and when the comparator is facing east or west. The same is when it is not in subtract mode.