[Arm-dev] Silly question about expanding the root directory

I've been having serious issues trying to expand the file system in userland 7 on large micro-sd's. No problem with 32Gb or smaller but expanding a 64Gb or 128Gb turns the system into a brick and I have to rewrite the install image. Before expanding, the systems run fine on the large (mostly unused) micro-sd cards... Tried this on both Pi2 and Pi3. Ideas? What am I missing?

Thanks in advance for any advice...

-DM DigitalMechanic