INSERT SELECT not working with triggers.

To recreate the problem:

create table a (id bigint not null primary key, name varchar(30))

insert into parasql_pk_counters values ('a','id',5000) -- our way of managing simple counter - code unchanged for years

insert into a (id, name)

select parasql_next_val('a'), 'dog'

from Customers -- just a table with some records

limit 10

select * from a

The above code works as expected when table a does not have a BEFORE insert nor BEFORE update trigger. Adding either trigger (even if it does nothing) results in:

ERROR: (conn=50) Column 'id' cannot be null

Prior to v10.11.11 everything worked as expected for years.
After updating from 10.11.10 to v10.11.11 the problem is as follows:

If table a has no triggers - works as expected
Adding empty triggers (with just a comment):
BEFORE insert = ERROR: (conn=50) Column 'id' cannot be null
BEFORE update = ERROR: (conn=80) Column 'id' cannot be null
AFTER insert = works as expected
AFTER update = works as expected

This seems similar to MDEV-36026 - Problem with INSERT SELECT on NOT NULL columns, but I am not sure so submitting as new bug as both BEFORE insert and update cause the problem.