Comment 22 for bug 1396787

@spvkgn Thanks!

From the log it seems this is not a loop, just applying the very high cost fallback for each held package:
...
Checking: linux-generic ([<Origin component:'main' archive:'bionic-updates' origin:'Ubuntu' label:'Ubuntu' site:'ru.archive.ubuntu.com' isTrusted:True>, <Origin component:'main' archive:'bionic-security' origin:'Ubuntu' label:'Ubuntu' site:'ru.archive.ubuntu.com' isTrusted:True>])
package linux-generic upgradable but fails to be marked for upgrade (E:Unable to correct problems, you have held broken packages.)
falling back to marking linux-generic, then adjusting changes
package linux-generic upgradable but fails to be marked for upgrade (E:Unable to correct problems, you have held broken packages.)
falling back to adjusting all packages
adjusting candidate version: 2ping=4.1-1
...
package linux-generic upgradable but fails to be marked for upgrade (E:Unable to correct problems, you have held broken packages.)
sanity check failed for: set()
Checking: linux-headers-generic ([<Origin component:'main' archive:'bionic-updates' origin:'Ubuntu' label:'Ubuntu' site:'ru.archive.ubuntu.com' isTrusted:True>, <Origin component:'main' archive:'bionic-security' origin:'Ubuntu' label:'Ubuntu' site:'ru.archive.ubuntu.com' isTrusted:True>])
package linux-headers-generic upgradable but fails to be marked for upgrade (E:Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.)
falling back to marking linux-headers-generic, then adjusting changes
package linux-headers-generic upgradable but fails to be marked for upgrade (E:Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.)
falling back to adjusting all packages
...

This is still a serious problem and opened a separate bug for it, but seems much better than an infinite loop.
Can you please confirm that finally u-u finishes processing the packages?