hi jason w, hi tinypoodle,
i can confirm that microcore 5.0.2 has the same buggy behavior, so probably it's a kernel problem.
i used the same configuration, the same mydata.tgz.bfe, the same loaded extensions, the same bootcodes,
only core.gz, modules.gz, rootfs.gz and vmlinuz are taken from 5.0.2 and the resume from ram fails.
with core.gz and vmlinuz from 4.7.7 everything wakes up flawless after suspend to ram.
thank you for all your contributions.