What about those combinations for which planner didn't went into planning book? The reason seems to be the same as you can see the forecast in planning book (coz of default macro, when you go in for analysis) but is not shifted to ECC as planner might not have even visited the planning book (and as per your statement: "In some cases, it occurs that the forecast value displayed in SDP94 and saved is not correctly sent to ECC".
The above is again directing towards the same cause.
I would suggest you to put a job in the background (for similar macro) for calculating the forecast before releasing it to ECC. This should resolve your issue.
Regards
Rahul