- [x] I looked for a similar issue and couldn't find any.
- [x] I tried with the latest version of GPAC.
- [x] I give enough information for contributors to reproduce my issue (meaningful title, github labels, platform and compiler, command-line ...).

Hi,

For the provided test input, `MP4Box -bt issue-2137 -std` would produce inconsistent results. To reproduce:
- gpac: git head at the time of report (commit 595e437b3de00bce23d09306d23fbc891334e241)
- Compile gpac with `-O0` and `-O3` with either gcc or clang. 
- Run `MP4Box-O0 -bt issue-2137 -std > out-O0.txt` and `MP4Box-O3 -bt issue-2137 -std > out-O3.txt`. 
[issue-2137.tar.gz](https://github.com/gpac/gpac/files/8215398/issue-2137.tar.gz)

- Here are the diff result:
```
$ diff out-O0.txt out-O3.txt
65,66c65,66
<     fromTo 0.00392157 3.60988e-38
<     key [4.03322e-41 0 0 0 0 4.50097e-42]
---
>     fromTo 0 0
>     key [0 0 0 0 0 0]
```
I tried to check with AddressSanitizer, UndefinedSanitizer, and MemorySanitizer, none of them complained.
Inconsistent/incorrect "fromTo" and "key" values produced by `MP4Box -bt`
This is a GitHub Issue
repo:gpac
owner:gpac
Title : Inconsistent/incorrect "fromTo" and "key" values produced by `MP4Box -bt`
Issue date:

--- start body ---
- [x] I looked for a similar issue and couldn't find any.
- [x] I tried with the latest version of GPAC.
- [x] I give enough information for contributors to reproduce my issue (meaningful title, github labels, platform and compiler, command-line ...).

Hi,

For the provided test input, `MP4Box -bt issue-2137 -std` would produce inconsistent results. To reproduce:
- gpac: git head at the time of report (commit 595e437b3de00bce23d09306d23fbc891334e241)
- Compile gpac with `-O0` and `-O3` with either gcc or clang. 
- Run `MP4Box-O0 -bt issue-2137 -std > out-O0.txt` and `MP4Box-O3 -bt issue-2137 -std > out-O3.txt`. 
[issue-2137.tar.gz](https://github.com/gpac/gpac/files/8215398/issue-2137.tar.gz)

- Here are the diff result:
```
$ diff out-O0.txt out-O3.txt
65,66c65,66
<     fromTo 0.00392157 3.60988e-38
<     key [4.03322e-41 0 0 0 0 4.50097e-42]
---
>     fromTo 0 0
>     key [0 0 0 0 0 0]
```
I tried to check with AddressSanitizer, UndefinedSanitizer, and MemorySanitizer, none of them complained.
--- end body ---
