Running out of ammo can mean a number of things:

-Lacking physical shells in inventory ("we've run out")

-Consuming shells much faster than they can be replaced ("we're running out")

-Lacking shells in the correct places to service the targets requested ("we're running out of shells here")

The latter is very likely given HIMARS related "smoking accidents" in Russian ammo stores that are too close to the front lines, or are large enough to be worth a GMLRS rocket or two. Small, distributed stores further from the front are more protected, but less efficient in delivering shells into tubes.

"Usage faster than production" is almost inevitable for any weapon system in high intensity wartime unless there is a heavy shift to a war economy. The question isn't whether country X will run out of weapons system Y, it's when will they. Usage and destruction factor into this too. The pressing issue here also becomes which type of weapon system is depleted first, for example 152mm Krasnopol is much more capable than a dumb 152mm.