Power issue

[garry]

Disconnecting the neutral is dangerous and could cause a severe shock situation so do not use it in that configuration.
Could be a bad dog bone.
With power disconnected look into your breaker box and make sure the ground and neutral are not connected to the same terminal strip.

As someone said with electric water heater could have a have a bad element unplug heater and try again.

Ground and neutral should not be connected in the RV.

[TG Twinkie]

In reading up on 50 amp GFCI breakers. Learn something new every day. Never had a hot tub.
In my interpretation of the info.
The GFCI must be located in a 4 wire panel. Meaning there is no bonding of the neutral.
Are you trying to use an existing breaker previously used for a hot tub?
Did you wire the GFCI breaker?
Where is the white curly wire from the GFCI connected?
Where is the neutral wire from the 50 receptacle connected?
Does the panel where the GFCI is located have a separate neutral buss?
Is that neutral buss bonded with a screw going thru to the back plane?