Unregular reading when reading the whole screen

[Hermann]

Hi,
I observed a strange phenomenon: When I read text by pressing the 
numpad-plus key, the text is read unregularly: Letters and/or sillables were 
omitted - it seems as if the speech have swallowed them - and words get 
pulled together in one, although they are written correctly.
Reading line by line does not show this. Checking the text in braille shows 
no typos. Especially it happens on webpages (read with w3m), but also in 
text editors, but less often.
I use Speakup with Espeak 1.25 via Speech-dispatcher and speechd-up.
Is this known? 
Hermann