Minecraft – ny other way to obtain Pumpkin seeds

It looks to me that it isn't a bug that's causing the seeds to pop out, but your lack of lighting. If an area is too dark, seeds will pop out. I don't know why the other one pops out too, but you can at least try to increase the lighting. That should fix the problem.

Squares with grey and red/grey triangles in them

These represent Redstone Repeaters.

The direction that the arrow points indicates the direction of the repeater's input/output, with the input being the flat end and the output being the pointy end.

You may notice that the triangle has four 'tiers', with each tier being either red or grey. Redstone Repeaters have four tick delay settings, so the more red tiers there are, the longer the tick delay setting:

That indicates a Redstone Repeater with a 1 tick delay outputting to the east, whereas this:

Indicates a 3 tick delay Redstone Repeater outputting to the east.

How light or dark the red is indicates whether the repeater has a redstone current in its idle state. The two examples above both indicate that the repeater has no redstone current when idle, whereas this:

Indicates a 4 tick delay repeater that outputs to the south and is receiving a redstone current in its idle state.

The same rules apply for yellow and grey backgrounds as for everything else so I won't cover those.

Personally I find this style of repeater easier to read at a glance than the current 'official' way of indicating a redstone repeater, which is like so:

Which would be a 1 tick delay active repeater outputting to the east.