[Bug] Internal consistency error: Incorrectly freed register in arg list

Compiling the following gives a consistency error

import meshtools
import constants

fn mobius(r = 1, ratio = 0.5) {
    var L = 2*r*ratio // Separation
    var m = AreaMesh(fn(u,v) mobiusfn(u,v,r=r,ntwist=-1), -Pi..Pi:Pi/20,-L/2..L/2:L/10, closed=[false,false])
    return m
}
fn mobiusfn(u,v, r = 1, ntwist=1){
    var th = Matrix([cos(u), 0, sin(u)])
    var twist = (cos(0.5*ntwist*u)*th + sin(0.5*ntwist*u)*Matrix([0,1,0]))
    return r*th + v*twist
}

--Registers (7 in use)
r0 mobius [0]
r1 r [0] (captured)
r2 ratio [0]
r3 L [1]
r4 m [1]
r5 temporary [1]
r6 mobiusfn [1]
--End registers
Internal consistency error: Please contact developer. [Explanation: Incorrectly freed registers in compiling argument list.].

Reproduction script:
newconsitency.zip

Start by running the provided newconsitency.zip reproduction script and tracing the compiler's argument-list handling when it reports incorrectly freed registers. Use the register dump and the failing Morpho example to identify the affected path. Done means the example compiles without the internal consistency error and register tracking remains consistent.