Error importing secret key

[wkuz at op.pl]

Hello!
Some time ago I have made a backup of my secret key and all the
subkeys, and then deleted by-hand the master secret key by

	rm ~/.gnupg/private-keys-v1.d/[keygrip].key

The subkeys were moved to a yubikey. Everything was great. Now I wanted
to import my master key for a moment... and here we have a problem.
Right now what happens, after running

	gpg --import secret_key.asc

is:

	1) gpg complains:

	gpg: key D444252908A80B6D: "sxrmn" not changed
	gpg: key D444252908A80B6D/D444252908A80B6D: error sending to
	agent: Invalid argument
	gpg: key D444252908A80B6D: secret key
	imported
	gpg: Total number processed: 1
	gpg: unchanged: 1
	gpg: secret keys read: 1
	gpg: secret keys unchanged: 1

	2) gpg -K is aware of the master secret key, though it says
	it's not there:

	sec#  ed25519 2022-07-06 [SC]
      	902404424B39514B6126A2F2D444252908A80B6D
	uid    [   absolutne   ] sxrmn
	ssb>  cv25519 2022-07-06 [E]
	ssb>  ed25519 2022-07-06 [S]

	3) seret subkeys get imported (now they are back on yubikey,
	but they got imported OK)

So... any ideas why this happens and what can I do about it?

-- 
xWK