[SalesForce] The record couldn’t be saved because it failed to trigger a flow – Process Builder

I have one Process Builder which helps me to do certain things on my Opportunity create/update and all.

Now, the problem is I have written one Trigger on Opportunity which is expected to run "After Update" while checking certain conditions and business logic following the same.

Check out the following Screenshot – for more detailed error message.

Any Suggestions ? or help ?

I have found following as Known Issue 1 and Known Issue 2. This might help to answer.

Updated Question :

My Trigger is also getting called too many times where I found
Trigger.new() = Null

Debug Logs

08:43:49.437 (5437733373)|EXCEPTION_THROWN|[37]|System.DmlException:
Insert failed. First exception on row 0; first error:
CANNOT_EXECUTE_FLOW_TRIGGER, The record couldn’t be saved because it
failed to trigger a flow.
A flow trigger failed to execute the
flow with version ID 301110000000ZDe.
Contact your administrator
for help.: []

08:43:49.439 (5439388332)|FATAL_ERROR|System.DmlException: Insert
failed. First exception on row 0; first error:
CANNOT_EXECUTE_FLOW_TRIGGER, The record couldn’t be saved because it
failed to trigger a flow.
A flow trigger failed to execute the
flow with version ID 301110000000ZDe.
Contact your administrator
for help.: []