The issue of reloading time for the M109G

I find it strange that the reload time of the M109G is several seconds slower than the M109A1 (13.3 seconds by default for the M109A1, but 17.3 seconds for the M109G). The layout of the vehicle is almost identical, and the same can be said about the ammunition used and the number of crew members. Curiously, the default loading time of the M109A1 and the ace crew loading time of the 109G match (both 13.3 seconds), and this issue could be a bug.

It isn’t. The M109A1 has a different gun with a mechanically assisted loading system. The basic M109/M109G has a shorter gun without the loading system. It is the same longer reload for both M109Gs and the Israeli M109.

Hopefully the M109G is just a stop gap for other howitzers like the PzH2000.
Pretty sure the loading system is different. But Escargot probably implemented it as is with balance being a justification.