EWM outbound delivery document flow not updated

[Chethan_tv]

Hello Experts,

I have seen this issue quite often, however not able to understand the main cause of it.
Document flow such as PCP (picking plan) or PCA (picking) is not updating in delivery document flow.

For instance, with respect to PCA link: The stock removal warehouse task is already confirmed, the stock has the corresponding reference, but the ODO item has only a PCP link, a corresponding PCA link is not available.

I am aware of how to fix this via EWM check monitor. However, to fix this permanently I am not able to reproduce this or not able to understand main cause for this. 
Any input is really useful, thank you.