There is no doubt that the mobula7 as reviewed here is an excellent quadcopter that has redefined what ducted micros can achieve at a fair price but the key flaw in this model (and other ducted quads) is lack of durability in the frame. Frames for the Mobula are not expensive at $4 here but waiting on a frame to be delivered represents downtime.
Welder's glue is often recommended but is not available everywhere and shipping can be precarious on this. I tried the E6000 glue from banggood on a whim and am really please to report it works perfectly, is inexpensive and being available from Banggood, is available worldwide. It comes 15ml, 50ml and 110ml tubes for $3, $4 and $7 repsectively at time of writing. 15ml is plenty for the small amount we need for repairs. It also has a very fine metal nozzle which is just perfect for the fine work we do on repairs. The cap has an integrated pin that sits inside the nozzle for storage so never blocks.