I think that the reason they told us the full mask would not help is that they are a volume shop, and seek to eliminate marginal costs.
The first bipap we had broke with error code E53, and they replaced it.
I might be able to nap or sleep with the bipap. However, there are two remaining major problems:
1. The inhale/exhale cycle is highly variable and erratic. Sometimes the inhale period is one full second, but very often it is 1/5 to 1/2 of a second. I think it quite likely they will say this is impossible, or blame us, but I wear it, and I know.
2. The alarm sounds every few minutes.