my mazda demio new showing HOLD light and failing to engage gear 3

What is your question?

the mechanic told me that it was the gear box back plate which needs to be replaced,got the gear box cover plate replaced and the problem dissapeared. The next day as i was travelling to work the hold light suddenly re-appeared and now its re-appearing and disapearing.What could be the problem

What makes this problem better or worse?

its worse when engine is cold

How long has your 2011 Mazda 2 had this problem?

a few days