Parity controls break when both inside and outside a custom gate

[Strilanc]

Example:

https://algassert.com/quirk#circuit=%7B%22cols%22%3A%5B%5B%22zpar%22%2C%22zpar%22%2C%22~14b2%22%5D%5D%2C%22gates%22%3A%5B%7B%22id%22%3A%22~14b2%22%2C%22circuit%22%3A%7B%22cols%22%3A%5B%5B%22zpar%22%2C%22zpar%22%2C%22X%22%5D%5D%7D%7D%5D%7D

ERROR OBJECT
Error: Exactly one parity bit must be in the inclusion mask
Details: {"inclusionMask": 5, "parityMask": 15}

ERROR LOCATION
Error
at new n (https://algassert.com/quirk:363:72014)
at new n (https://algassert.com/quirk:363:169303)
at n.and (https://algassert.com/quirk:363:170701)
at n (https://algassert.com/quirk:363:133847)
at t (https://algassert.com/quirk:363:132508)
at https://algassert.com/quirk:363:131978
at t._applyOpsInCol (https://algassert.com/quirk:363:152035)
at t.applyMainOperationsInCol (https://algassert.com/quirk:363:151183)
at n (https://algassert.com/quirk:363:134170)
at t (https://algassert.com/quirk:363:132508)