App Crashes when open & close PDF multiple times

When I repeats opening different PDF files, it occassionally crashes as follow:

12-15 12:33:45.088 11385-11929/hk.hku.versitech.eform A/libc﹕ invalid address or address of corrupt block 0x7988cd90 passed to dlfree
12-15 12:33:45.088 11385-11929/hk.hku.versitech.eform A/libc﹕ Fatal signal 11 (SIGSEGV) at 0xdeadbaad (code=1), thread 11929 (Thread-3847)

For every time opening a new PDF file, I invoked and then create a new PDFReader object to open

attached core dump (crash.txt)
Any way to troubleshoot for the problem?

i'm using PDFLayoutAct, seems no problems.
are u using demo project?

I'm not using the demo, but using my own activity to open PDF file.
I created a new PDFReader instance and opened a new PDF file immediately after calling pdfReader.PDFClose();
would that be the cause?

maybe, PDFThumbView has problems.
plz wait next version.

what is the codes to open and close?
includ thumb view or other attach the Document object.
mostly, it caused by Invoke Page.Close() after Doument.Close().

Here's the relevant code attached.
When trying to open a file, MyActivity.loadFormAsync(path) will be called.