Erratic passphrase recognition (gpg (GnuPG/MacGPG2) 2.0.17)

[Rembrandt Wolpert]

I am new to gpg -- and I am confronted by a weird, erratic behaviour
of gpg: sometimes it recognises my passphrase, sometimes (alas, a lot
of the time!) it doesn't. Since I can make the passphrase in pinentry
visible I know that I am making no typing mistake. Any advice what I
should do?

Many thanks,
Rembrandt

PS. It just right now doesn't let me sign this email...
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