Odd results when existing capacity data doesn't match the time framework [BUG]

One of the tutorials talks about changing the time framework to every 2 years instead of every 5 years. According to the tutorial, this is a simple matter of changing the settings file, and doesn't involve changing any of the timing data in the csv files. Even though the existing capacity is specified every 5 years, MUSE should carry out linear interpolation and everything should still be fine with a 2-year framework, right?

Annoyingly this doesn't seem to be the case. If I switch the time framework to every two years without changing the capacity files, I get a very strange result in the gas sector:


If I interpolate the capacity files myself (to create a new set of files matching the new time framework), and then re-run the model, it looks much more reasonable:


I have no idea what the root cause of the issue is, but it seems like something is going wrong when the capacity data doesn't match up with the time framework (even though MUSE _should_ deal with this fine by interpolating the capacity data)

A couple of approaches:
- Enforce that the timing data in the capacity files must match the time framework specified in the settings file (and update the tutorial model accordingly)
- Find out what's causing the bug in this example and fix it