DHCP - ip configuration could not be reserved (no available address timeout etc.)

Using ESXi6.7 -

I have two guests    A and B  -  Guest A is a transparent bridge, it passes traffic, it also has a management port that i can assign using DHCP (or not)

1/ If i assign a port group to each and use DHCP to an external  upstream DHCP server. All works great for both guests.

2/ Assign static IP's , all day long - not a problem.

3/ If i try and have guest  B obtain a DHCP address via Guest A  with the internalonly port group it will;

   a/ Work 100% of time as long as Guest A  does not have an associated DHCP address it's obtained.

   b/ Will not work and get timeout when Guest A has it's ip address via DHCP

My question is:

Is there a restriction on the number of DHCP IP's a Guest can obtain and where is that  limiter?