can't seem to catch crystal skull - only persona remaining to achieve mask compendium and so platinum.. any tips?

[solomonluthor 12]

I've only got the crystal skull remaining as persona left to complete mask compendium. hve already finished all seven palaces and bosses except for final boss, but cant seem to catch the treasure demon - tried the shehiruth and treasure trap on floor 13 strategy multiple times, on multiple different days. 

 

will be much appreciated if someone could give tips - so annoying that Ive now played over 140 hours on persona 5 and this one mask is keeping me away from my platinum on this game I love

[solomonluthor 12]

lol. and as soon as I put this on the forum, on the verge of giving up - the RNG gods take pity and give me one finally. This platinum is one that was a bit annoying - but I loved the game and the music so much, didn't mind going through it twice. tho some trophies (golden finger, mask compendium etc) nearly made me give up on the platinum lol