Today I solved the problem. It was my own stupidity.
When G43 is called, the interpreter will apply the tool offset not
in the next move but it applies the offset
by components - when the individual axes move. Therefore, since my program does not contain any Y-axis movements, the correction was never applied. Instead, once G43 was called, the axis immediately changed its position to -offset.
To fix it, I modified my post-processor to produce tool change like this:
