Scaffolding switches quickly between entity and block when placed on some non-solid blocks

Mm yes, thanks. The change was that they can't be placed directly atop

I think the bug is trying to fix by not letting the scaffolding block be manually placed on those blocks... But when you drop the scaffolding block on them, the error occurs. It is not a solution, that the scaffolding block "skip" as an item would not be a solution either... the scaffolding would lose the scaffolding functionality, because, when building, for example, you could not put your scaffolding on a roof of stairs.

To be fair it is actually a solution to exactly what was described in the report, which only mentioned placing scaffolding on those blocks, not dropping the scaffolding on them. And since scaffolding requires an actual support to be placed on, preventing its placement on those blocks fixes half of the issue and makes scaffolding work more like how it's supposed to.

The error reported here is only about placing blocks, but some other reports which are linked as duplicates to this report are about falling scaffolding blocks, e.g. MC-139388. Is it more related to MC-90523 perhaps?

The obvious options regarding falling scaffolding blocks are:

• Keep current behavior, with scaffolding blocks floating and glitching until the below block is mined.
  Possibly fix this and related issues with other falling blocks at some point.

• Turn the falling scaffolding block into a solid/resting block one block above the reported blocks (end rods, stairs etc.).
  Physically not very believable to do so for many of these blocks.

• Drop the scaffolding block as item, like it does if it falls onto e.g. a torch.
  This would prevent "forever" floating scaffolding blocks (is this a performance issue for clients or servers?).
  The same behavior may or may not be desired for other blocks like sand falling onto a fence or wall, as reported in MC-90523 (some farm designs make use of floating sand IIRC, to catch/destroy projectiles or something like that)

Confirmed SNAPSHOT 18W47A/B & 18W48A/B

maybe consider removing the crazy restrictions and just let us use scaffolding, restrictions as of 18w48b will only do 1 thing: it wont be used as scaffold but as nice looking tables and shelfs. removing the ability to place a scaffold on the side of blocks makes them even more useless than before...

 Confirmed SNAPSHOT 19w03a

Fixed in 19w07a.

seems to be blocked by some bug that enables you to place scaffolding beyond distance 6 atached to another scaffolding (posibly due to fix of MC-143687) because of that, now you can no longer create a falling block entity of scaffolding in survival 

When you place an end rod and stand on it and use /setblock ~ ~ ~ minecraft:scaffolding the scaffolding break immediatly.

Using /setblock does seem to show that the scaffolding now breaks, but I'd rather wait until MC-144096 is fixed so this can be tested without the use of commands.

Not fixed in 19w11a.

Confirmed as a problem in 19w11b. I've attached a video of a stack of scaffolding on top of Oak Stairs, however, they keep turning into entities. This also causes some fairly poor FPS drops due to the physics blocks.

Confirmed in 19w12a.