Where's the best place to farm Cloister Map Fragments?

[zim.ha]

Anyone know where's the best place to farm Cloister Map Fragments? I try to go on Lab 6 in dungeons which is somewhat challenging for me but I only meet up with invaders about 2 times in every 5 runs. Is there a different chance of invaders invading in different dungeons? Are there any dungeons that have a higher chance of invaders? Looking forward to your replies!

[Skyros]

NTT (Nameless Tyrant Tomb) is the new rave today. It was bugged before and I feel like its fixed now. Still, there are a lot of people running NTT because they say it has a higher spawn rate (although based on recent experience, Invaders appear like half of the time).

[Lans Vahndreas]

Sometimes in Nameless Tyrant Tomb, I didn't meet any invaders even it's LB7+ with the Board Quest.

[Skyros]

And thus the 'I feel like is fixed'. As per experience, before the current patch its almost a 100% invader spawn rate.