WHEN I EDIT MY SIGNATURE AND SAVE THE CHANGES, THE OLD SIGNATURE KEEPS
APPEARING.

Details:
In the settings, I had created a signature, which is no longer true,
and I really need to change it.
So I have edited the signature to say the up-to-date info, and, of
course,  I did click the button "Save the changes" and waited till it
happens.

But then, when I compose a message, the OLD (deleted, and retyped)
signature persistently keeps appearing at the bottom of the message.
Recently, I tried to compose immediatelly after editing the settings
and the signature appeared right. But, at the (soon following, during
same session) second instance of composing, the old signature crept in
again. I do not understand how it happens. And, when I go AGAIN to
settings and open it, the old signature is written there, as if I
changed nothing!   But I DID (the appearing of the right signature
once, is the proof).
Anyone can help me to get rid of this strange system problem?

I tried several times (within one week) and still the same!