Version of mod: 4.9.1.92
Part of modpack: FTB Ultimate Reloaded v1.6.0

The issue involves blockplacers (projectred), timers (projectred), and blocks that when placed are a forge multipart. When a blockplacer is powered by a projectred timer to place a Forge multipart block such as a cover, a project red frame or a gate. It will use one item and place a "ghost" block which appears to just be part of the mesh and not actually added to the chunk. Reloading the map, placing a block in the ghost block or just waiting will cause the block to disapear. Once there is a "ghost" block the second activation of the blockplacer will place an actual block. This behaviour is not seen if a vanilla repeater is placed between the blockplacer and the timer. I encountered this issue whilst playing on my laptop with a core i5-8250u processor and integrated graphics with 8gb of ram which becomes quite toasty. It is possible that the issue does not happen on a slightly more powerful computer but I have not tested that scenario.

In the following link you should find a savegame of the setup and picturers of the setup that causes the bug

https://drive.google.com/drive/folders/1BY_HxSui01zUTLouV7AwaExle0pdTn_c?usp=sharing

Its extremely strange as to why the repeater works but the timer does not. Could be related to the way the timer causes block updates. Can you re-provide your setup? The link seems to be broken.

Am able to reproduce strange placement of multipart items when ticked with Timer gates. Seems to be mitigated by placing a Repeater before the Block Placer. Will investigate further.

1613b90 will at least stop the block placer from placing a Multipart version of the frame block when not needed.