Books from the main inventory cannot be used when My Warehouse is open

I'm not yet sure what are the repro steps, but I've noticed that happening to me several times after the inventory update:
1. Open My Warehouse
2. Click on an EXP book (e.g. Ancient Book of Intelligence (All)) in your main inventory
3. Observe "You cannot use this yet. Please try again later." message. Will goes down by 10%.
4. Go to step 2
You can click on the book until you run out of will, but it would not get used.

Closing My Warehouse and opening Inventory lets you use the book normally.