LaTeX introduces non-existent excess space on pdf insertion - pdf

Question

I try to insert a PDF file into my LaTeX document. It is properly cropped (by using the "Inkscape trick") and should easily be inserted without a problem.
LaTeX however, introduces a huge white space in the document which forces itself to create a "blank" extra page just to fit the PDF to the pages.
Just like this:
This is the code creating the problem.
\end{minipage}
... % Other code
\pagebreak
\subsection[Diagramm]{\uline{Diagramm}}
\vspace{-15pt}
\begin{figure}[H]
\centering
\includegraphics[height=0.98\textheight]{Abbildungen/ASMD_Diagramm_v2_X.pdf}
\caption{ASMD-Diagramm}
\label{Fig ASMD-Diagramm}
\end{figure}
... % Other code
\pagebreak
Now I have another PDF which is inserted properly and exactly as expected.
I have tried the following already:
Recrop the PDF
Using the trim command of \includegraphics
Resizing
Using other file formats (all were not satisfactory)
To be honest I don't know much about LaTeX and am more of a beginner-intermediate user than someone who really know this stuff. But this bothers me and has bothered me for quite a long time already. Anyone has any idea on how to fix this or what I am doing wrong?
Thank you!

Answer 1

Solved the problem. As discussed with samcarter, the space around the pdf file in the document seems to have been too small, so LaTeX couldn't accomodate for the caption, header, etc.
By trial and error, I just changed the size from:
...
\includegraphics[height=0.98\textheight]{Abbildungen/ASMD_Diagramm_v2_X.pdf}
...
to
...
\includegraphics[height=0.95\textheight]{Abbildungen/ASMD_Diagramm_v2_X.pdf}
...
and now it fits quite well on the page.