It sounds like this has to do with your Inventory Allocation Priorities, but there's a lot of different parameters that go into replenishment allocation calculations. I'm assuming that you'd like to replenish an entire pallet at a time in these locations. First, you should check the max quantity on the location, and make sure that it's at least as much as a full pallet quantity of whatever sku you have slotted there.
When calculating the space available in the location, from what I've seen, it calculates MAX_INVN_QTY - ACTL_INVN_QTY - TO_BE_PIKD_QTY + TO_BE_FILLD_QTY. So, say your location holds 50 units (which is a full pallet quantity), and there are 10 units currently in the location, and 0 TBP and 0 TBF. If you run a wave that picks up orders for 15 units, then it'll need to generate a replen because there's only 10 units there. It'll calculate that there's space available for 40 units, i.e. less than a full pallet. Assuming you have your system configured to replenish up to the max quantity and combine priority 40/50 replens, it'll generate a priority 40 replen for 40 units because it thinks you can't fit a full pallet.
What you could do is set your max quantity to 99 (2 times the full pallet quantity minus 1 unit). This way, there will never be enough room available to generate a replen for 2 pallets, but as soon as you pick 1 unit, there will always be room to replen 1 full pallet. Then, in your inventory allocation priorities, add a rule that allocates replens from reserve for these locations, but set the Allocation UOM to Pallet. Make sure that any rules you have that allocate in less than pallet quantities don't see these locations, so you might have to create a couple of Allocation Rules to go along with your Allocation Priorities. This way, using the above example, it'd calculate that it needs to replenish 89 units instead of 40 units. With a pallet quantity of 50 units, it'll be able to replenish 1 full pallet. It'll then look to allocate the remaining 39 units, but if it can't allocate in units or case quantities for those locations, it'll fail, and it'll only replenish the 1 full pallet.
A potential issue with that is if you don't have any full pallets in reserve, but you do have a few cases here and there on mixed pallets. Those won't get allocated. Also, if you happen to have a full pallet of 50 units, plus another pallet of 39 units, then it'll allocate both. That's because when you use Allocation UOM = Pallet, it'll look for a pallet that has only that sku on it, regardless of how much of that sku it has. That is, if there's a pallet that contains only 1 unit of that sku and nothing else, it'll consider that when allocating in pallets.