Project saved with ML is hanging v2.1.5 when loading it.

[micheus]

around 25000 vertices, but with 4 or 5 2048x2048 textures

It's hard to say something without experience that.
Did you try to use the ML (since you says it loads your file) to disable (remove) the textures and try to load the plan mesh only in the 2.1.5.
Are the textures internal or external?

p.s. I'm going to move soon these posts to the bug reports session.