I've detailed this bug report here: AstralOrdana/Spelunkery#301
Just posting it here as well in case a solution could be implemented on your end.

the only thing i can really do about it is allow crying obsidian as a valid frame block for infinity portal blocks. the code placing crying obsidian is out of my reach

Is there no way to “cancel” the event of the nether portal breaking?

Spent some time looking into this, unfortunately even allowing crying obsidian as a valid portal frame doesn't work. I would recommend disabling "Portal Destruction Crying Obsidian" until Spelunkery can fix this.

Alrighty, just waiting for them to reply then. I'll close this issue when it's fixed on their end.