Weighted pressure plates do not retain power level when items merge

Weighted pressure plates does not retain power while items are still on it.
This is the problem of a single item type. Similar to MC-29778.

On the attached pictures you can see 2 pressure plates, the on the left has 8 different items, the one on the right has 8 items of a single type.

Actual behaviour:
Left pressure plate retains the power of 8.
Right pressure plate flicks between the number of items and then goes back to 1

 

Expected behaviour:

Both pressure plates retain power if items are on it.

 

Steps to reproduce:

1. Place down Golden pressure plate with comparator (2020-11-16-12.21.32.png)
2. Throw 8 items on a pressure plate by quickly pressing Q (2020-11-16-12.21.37.png)
3. Observe power goes to 1
4. Power changes to 4 (random range between 1-8) (2020-11-16-12.21.39.png)
5. Power goes back down to 1 as entities merge in (2020-11-16-12.21.44.png)

Note: This has been observed on both Iron and Gold pressure plates.