I've never seen a DC relay hang up from residual magnetism.
The reason is the core material is intentionally a type that does not
retain magnetism. If it is magnetized, it will simply magnetize again.
The reason most relays hang-up is because they weld into position
from hot switching.
Lack of receive is more commonly caused by high resistance in
the contacts, which is generally caused because the contacts are
high current contacts designed to wipe when normal current
passes through the contact. Running a 20 ampere relay at nearly
zero amperes will almost certainly insure the relay will become
unreliable over a period of time.
That is a constant fight when using conventional high current relays
to switch receiving lines.
73, Tom W8JI
w8ji@contesting.com
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