Some more research.

However, the one in 0x174C falls into a region which isn't mapped out (unless I missed something). This region contains 24 groups of 32 bytes each, beginning at 0x150A and ending on 0x1809. ...

This turned out to be a wild goose chase. That area stores VFO parameters for the current band when you switch bands: here it remembers which parameters you used last time when you selected the same band. This isn't the problem.

I performed three experiments, and I believe they will show the way what's going wrong.

1) I did a factory reset on the radio and collected the image. (As Dan stated, the memory is mostly left unchanged by the reset; a lot of traces of my previous tests were left intact. It turned out to be fortunate.)

2) I imported my usual CSV file which programs 145.230 MHz, negative offset, 100Hz TSQL into channel 4 right into this freshly reset image. Observation: that import changed exactly one byte (0x2C4D, which enables channel 4 and applies a few other flags for it). Because the data from previous experiments was still there, nothing else changed. This image has the problem!

3) I manually programmed my usual 145.230, negative offset, 100Hz TSQL into the VFO, overwrote channel 4 with it, and retrieved the image. That image works normally! When compared with the one from above, it becomes clear that a lot more things were initialized by the radio (most notably within the 32 byte block beginning at 0x32EA, which is the data for channel 4).

Please see the three attached images.