If it still can help a few of you...
The issue is that 9 weeks are added instead of 8, so even the first week of may is filled with the programm of the last week of april.
The easiest solution I've found is to manually replace the date of 25.04 by 18.04 and the date of 02.05 by 25.04. You need to do it on two records of table lmm_meeting and on all records of table lmm_schedule. It's very easy and fast.
After updating the dates, I recommend deleting all entries since 09.05 on table lmm_schedule and after that you can import the may workbook again.
Enjoy the meetings!