Interpolation not working!

Master is compatible. I used smart playlist to check, in lieu of show master compatible function not working.

all nodes are matching.

I am not sure, why interpolation is not working.

Are you interpolating between those 4 masters?

that’s true

It seems to me that you can interpolate using only the the two masters at the extremes.
Have you set up your instances correctly?
See this tutorial:

It seems that the first master is empty?

First master is an instance.

I have added this is instance as master and re-interpolating it.

This is working for most other glyphs, but not for few glyphs.

This is solved. “enforce compatibility check” help locate the problem.
Although there were equal number of nodes. handles were not same one curve.

Many thanks. This tool is fantastic.

Why do you have so many masters. I’m pretty sure you can remove some and still get to the same results with the instances.