Submarines aborting attack on the surface

[rattovolante]

For 2 days in a row I have had submarines attacking unescorted transports on the surface, only to immediately abort the attack without firing a shot because they were "low on ammo". Combat animations show the message "SS RO-34 attacking on the surface" immediately followed by "SS RO-34 low on gun ammo, Ota, Takeshi breaks off surface engagement and submerges"

In the last turn this happened to two submarines, RO-34 and SS I-159, which tried to attack the same ship, xAKL Sibolga.

ship screen shows ammo as:
RO-34: 5/5 torpedoes, 12/18 8cm gun, 2/18 25mm gun
I-159: 2/2 torpedoes, 1/12 12cm gun

Remarks:
[*]the submarines still have their full torpedo load! is the "out of ammo" logic faulty?
[*]if xAKL Sibolga is not considered worthy of expending a torpedo volley (which is reasonable, considering I-159's volley is 8 torpedoes, a real overkill for a light cargo), and the submarines are considered to be "out of gun ammo" (but again, note that RO-34 still has 2/3 of its 8cm ammo), they shouldn't surface at all, as this reveals their presence in a PBeM

Pre-turn resolution save attached.

BTW, in order to chase xAKL Sibolga I-159 has reacted more than its max react range this turn, and by doing so has allowed its endurance to drop in the "red zone"... is this intended? Is max react calculated per phase or per day?