Android PDF lib not working on some tablets

Customers with "Empire Electronix" tablets are complaining that all PDF pages are white.
Most have the Empire Electronix M1009, I have obtained an Empire Electronix M785, it has the same problem.
I tried my own app, I tried the in-lib example activities, and I tried the Radaee PDF reader from the Play Store. All display white pages on every PDF I try, on this tablet.

is it possible to test Page.RenderToBMP directly?
we suspect, jvm is the problem.

In my app I use libPage.RenderToBmp(targetBitmap, displayMatrix);

I am not using the PDFReader class.

are RenderToBmp return false?
are Bitmap can't be RGBA_8888 format in some devices?
or check save Bitmap as image and check it?

maybe this is real reason:
stackoverflow.com/questions/11994129/col...rgba-8888-everywhere

Thank you for your response.
1. are RenderToBmp return false? => yes, false
2. are Bitmap can't be RGBA_8888 format in some devices? => [strike]I now also tried ARGB_4444, ALPHA_8 and RGB_565, same result.[/strike] Not sure if this test was done correctly.
3. or check save Bitmap as image and check it? => I did, the saved file is also completely white and has the size of a page in my app.
4. I tried with hardware accelaration off, same result
Note that the pages are white because my bitmap is cleared white (eraseColor(0xFFFFFFFF)) before I call RenderToBmp, just as you probably do in your app. Otherwiste the bitmap is transparent.