Updated descriptions by GoldenHelmet
In 1.16, pumpkin growth was changed so that stems no longer search all four sides for a suitable block to grow fruit on. Instead, stems choose a random side first, and then check if the block is suitable for fruit. (Intended behavior per the resolution of MCPE-90344.) If the block is not suitable, the growth attempt fails. This results in pumpkins growing much more slowly in many farms. In particular, farms where pumpkins are planted in double rows or rows with water or walls along one side have 1/4 the rate of production that they used to have. (Likely also intended behavior as it matches Java, reported at MCPE-109406)

The above parity changes failed to take into account that the chance of pumpkin stems making a growth attempt when ticked still uses the crop growth mechanic originally ported from Java, which has not been adjusted for Bedrock's lower default tick speed. That is, the chance of a pumpkin stem attempting to grow a pumpkin when ticked is

1 / ( floor ( 25 / GrowthSpeed ) + 1 )

whereas for crops it was adjusted to be

1 / ( floor ( 9 / GrowthSpeed ) + 1 )

As a result, pumpkin growth is now at least 67% slower on Bedrock than on Java. Moreover, I am not certain that Java even uses the crop growth mechanic anymore at all when ticking pumpkin stems; another mod suggested to me that stems make a growth attempt whenever they are ticked. If that is true, then the Bedrock growth rate could be more than 20 times slower in certain farm layouts.

Steps to reproduce

1. Plant pumpkins and melons in double rows, as shown in the attached picture.
2. Bonemeal all of the stems to complete their growth.
3. Set up adequate light for the pumpkin stems or set the world to "always day."
4. Wait for an hour.

Expected results

After an hour's time, nearly all stems would have produced fruit.

Actual results

After an hour, only about 1/4 of the stems produce fruit.

So I have a melon farm above ground, and it’s not automatic. It doesn’t grow any melons now since I updated to the nether update here a few days ago. It really Stressed me out because this was my only income for getting emeralds with villagers fast. please fix this ASAP, I’m playing on my iPhone 8 and it isn’t working whatsoever