Isn’t a bug.
Mermail abysspike’s effect is written WHEN/YOU CAN so it can loose the timing.
If its summon was performed during a chain 2 or higher,it loose the timing.
For example: the summon of abyssteus
•Reveal abyssteus chain link1
•Discart abysshilde as a cost
•Summon performed
•Abyssteus chain link1(or cl2)
•Abysshilde chain link2 (or cl1)
•Abysshilde summon abysspike
•Abyssteus add a level 4 or lower mermail monster.
Since it’s summoned inside a chain link2 or higher,regardless was chain link1 or chain link2 it’s effect vanno be activated.
In addition,this type of effects will loose the timing even if summoned in certain chain link1 effects:
The best example is mermail Abyssocea;
Since the summon of the monsters and sending the target monster aren’t concurrently,abysspike can’t activate it’s effect if summoned by abyssocea.