When I un-pallet items inserters will put multiple stacks into the Assembling machine. Inserters will not insert anymore until all are all used. They should replace the one that was used. This way there will always be 1 item ready to go. Like when you a crafting items. While Assembling machine it is crafting the item, the inserters are replacing the items that are needed.

ah, then it was not only my imagination ...
just recently (during the last 2 days) i found several mods that appeared to work really slowly with assemblers. having a closer look showed similar bahavior to what Soundra described, or even worse: only inputting one or several new items into an assembler when the output is completely empty. especially on combinations of longer crafting times with large amount of output items this adds quite a bit of waiting when the next item didn't start to be processed while the old output is still slowly being grabbed by inserters.
none of all those mods seemed to use the usual "buffers" on input and output (roughly twice the amount of required items on input as well as twice the capacity in output before the machine stops production)

hmm yea very strange. I think they changed how assembler output works slightly in v0.16. If it outputs multiple stacks, I think it is ok, but it is kind of ugly :( I can try to get it working.

I changed how stacks are output in the new v0.16.3 version, they might help with this issue! Let me know if it doesn't help

It works better, less of a downtime for the inserters.
Thanks