You are being too picky. Mondince is probably one of the better sellers to work with on the lower end of the price spectrum, but they're still 1/3 - 1/4 the price of the higher end Chinese frame companies such as XMCS, Lightcarbon, Winspace, Quickpro, etc. They do a good job in my experience - when I had an issue with the saddle clamp for the offset seat post that my FM336 came  with I reached out to Jack for replacement hardware since the issue was one of the cross/barrel nuts. Jack ended up sending me replacement hardware as well as an entire zero offset seat post for free that got to me within a week. Are the brake mounting posts perfectly flat and pristine on my frame and fork? No, but they were masked well during painting and flat enough to have minimal rub. I ordered a facing tool to improve them, but it's such a minor problem I haven't felt the urge to face them just yet.

The rivets are a miss, yes. I would've been interested in hearing how they address that but it sounds like you'd be better served by one of the bigger players. I think for those looking for quality frames in the $500-800 range that may require a small amount of finishing work Mondince is a better option than SPCycle, Meinier, Seraph, etc. Light Cycling seems promising, but no one has built one up yet so the verdict is still out for them.

I get that these are cheap frames, but if you as a vendor can't keep your word and struggle to manage all the different orders, then just don't promise things and say it will be perfect. It's better to say "no, we can't" or "we won't". It's as simple as that.

What was on your list of things to check? Bottom Bracket, brake mounts etc.?

Yes, nothing complicated, just the basic stuff to make sure they actually check for it. And I asked them to weigh the finished frame and fork, should get photos soon-ish.

I had already cancelled my order after Jack told me it will take significantly more time than he initially said. But a day later he send a picture of my frame, saying it can ship on sunday and offered a small discount if i reconsider. I did and tracking shows the frame is on its way since monday. I expect it to be at my door next week.

I hope it's not my frame they sent you  Anyway, let us know how it will turn out. Mine should be sent this week. 'Jack' told me delay was because of some issues they had with paint quality. 

I'd really love to see that picture ^^
I'm still unsure about the colour for that, seeing some real frames would definitely help a bit.

Sure, but I doubt it will help you much.

Just forget you've ordered the frame and chill. That's what I'm doing. It's not like you're buying a $3k Specialized frameset from an authorized dealer. I'm sure Jack, or whatever his true name is, will eventually get back to you with the video of your freshly painted frame.

I was set on FM366, but FM376 immediately just has a better vibe about it.
Ordered it in size M, UD raw carbon high-gloss finish, no rivets on fork and rear triangle. Who needs those extra 50g. Price with Shipping to EU €632. Should receive it mid September.

Intersting. I've tried some image measuring tools, and I get somewhat close numbers to the new geometry (although I wouldn't call my quick method very precise  ), so I guess my eyes were deceiving me.

After a few more messages with Mondince trying to clarify what's up with that frame, it seems that your eyes are fine and it is NOT actually a new geo frame, quote: "It is the old geometry. But the frame is the same shape", even though a few messages back they have just said that "This is the new geometry" 
It's beyond me why would they even send photos of the prototype frame at this point and add to the confusion. I guess some things just get lost in translation or I am just not used dealing with Chinese vendors.
They said size M is already made so I'm trying to get the actual photos.

Here is FM366 in size M with 2.25" tyres. Would probably fit 2.35" by the looks of it. I got photos today and Mondince confirmed it's a frame built on a "new" geo.
But am I being crazy or something about the frame looks off? It might be a visual illusion because of chimney worth of spacers, a paint choice, or just chunky tyres, but to me it looks short, tall and too front heavy.
It's most likely just me being too undecisive about the frameset I want, but I'd love to hear opinions from more established gravel enjoyers. 



Did some AI "editing". I guess it does look better with less spacers and in a different paint scheme?..



EDIT

It is NOT actually a new geo.

I will add that for EU it's 750 Eur with shipping included.
Photos in the current listing are of the frame "before the geometry change, but the same shape'.
Max 46t chainring.