In year 2011, the problem of "ghost notes" was discussed in the Pianoteq Forum.  Its solution involved a replacement of midi cables.  I believe the HP203 has both a USB port and separate Midi In and Out ports.  If you have extra midi cables or an extra USB cable, you might try swapping these out, and checking whether that nasty E3 note has stopped sending a note-on message when no keyboard note was physically pressed.

Here's the URL to the Pianoteq Forum thread from 2011:

http://www.forum-pianoteq.com/viewtopic.php?id=1913

Hope this helps,

Cheers,

Joe

I've checked the MIDI events and the extra event comes in the middle of a bunch of pedal events, and it has the same velocity of the pedal event at the time:

ch1  Controller 64  value:78 (pedal)
19.434 ch5  Controller 64  value:78 (pedal)
19.444 ch3  Controller 64  value:78 (pedal)
19.444 ch1  Controller 64  value:71 (pedal)
19.444 ch5  Controller 64  value:71 (pedal)
19.444 ch3  Controller 64  value:71 (pedal)
19.444 ch1  Controller 64  value:65 (pedal)
19.444 ch5  Controller 64  value:65 (pedal)
19.444 ch3  Controller 64  value:65 (pedal)
19.444 ch1  Controller 64  value:59 (pedal)
19.444 ch1  Note 046 On (A#1) veloc: 67 (played)
19.454 ch1  Note 064 On (E3) veloc: 59 ( *** EXTRA EVENT ***)
19.454 ch3  Controller 64  value:59 (pedal)
19.454 ch1  Controller 64  value:48 (pedal)
19.454 ch5  Controller 64  value:48 (pedal)
19.454 ch3  Controller 64  value:48 (pedal).
... more pedal events ...
19.596 ch1  Note 046 Off (A#1) veloc: 96 (played note up)
...

The pedal event for ch 5 veloc 59 is missing - it would seem the Note On event is being sent instead?

I suspect the problem lies with the keyboard (Roland HP203). The no note-off event means that it keeps playing as long as it can or until I physically press the note again.

This only very rarely occurs - sometimes as little as once a month, although it happened twice this morning in a 5 minute period.

Any ideas anybody?