“Risks Involved in Starting Construction without a Signed Mortgage”

Let’s imagine a situation in which the self-promoter has half of PEC in own funds.
Let’s imagine that the start of the work for month X has already been signed with the builder, but the builder informs the developer that it is likely that it can start in month X-1 or X-2.
The self-developer doubts whether to move forward or wait to have the mortgage signed (and declaration of new construction) before the start of the works. The idea was to do the mortgage paperwork in those last 2 months before the start of the works.

Apart from the risk that for any reason the mortgage will not be granted, and then the work will stop halfway through, what other problems could there be for starting works without having a signed mortgage? Will the bank cause problems because the work has already begun, or does it not even have to know about it?

Greetings.