Could you tell me please how many repeated events can I set reminder for in zoho calendar?

I have 5-6 events that are repeated weekly, I set reminders "by email" on this events, but only some of them have reminders and I tried several times to set reminder for all these events but only 2-3 of them are getting reminders.

Please tell me what is the problem ?

Is this related with my free account or is it bug?

Thank's