Nether portal does not fully break when dispensing objects into it

When an object that breaks a nether portal is dispensed near the top corner, the nether portal may not fully break. Any block updates supplied to the portal will immediately fix this.

Steps to reproduce:

1. Create a large nether portal
2. Use a dispenser to dispense powdered snow into a block near the corner of the nether portal.

Expected result:

• The nether portal immediately and completely breaks

Observed result:

• The nether portal seems to break, except for a few blocks.