Batch 58 is showing the same odd checkpointing behaviour. This unit has reached 12.5% progress, properties show no checkpoint, checkpoint_debug flag is on now but no such message from this task in the event log yet, but stderr.txt gives this at the end (so far):

Setting up checkpointing ...
BOINC:: Worker startup.
Starting job S_0001
Finished job S_0001 in 615.359 seconds
Starting job S_0002

This is BETA_ beta26_ 00000058_ 0376_ 0--

"Checkpoint at most every" is still set to 300 sec.

At 20% progress, properties gives a checkpoint time, event log has this:

09/08/2017 20:36:10 | World Community Grid | [checkpoint] result BETA_beta26_00000058_0376_0 checkpointed

and stderr has this appended:

Finished job S_0002 in 481.844 seconds
Starting job S_0003

At this stage, boinc_checkpoint_count.txt appeared with content "1".

It looks like structure 1 is not triggering a checkpoint (or at least no evidence of one).

After completion of 9 out of the 10 structures in BETA_ beta26_ 00000058_ 0376_ 0, the boinc_checkpoint_count.txt was 8 and checkpoint_debug gave 8 instances of a checkpoint. It does seem that just structure 1 is failing to trigger a checkpoint. A variable being initialised wrongly or not at all?

Another question - does the final structure trigger a checkpoint, i.e. just before workunit completion?
Observation - BETA_ beta26_ 00000058_ 0376_ 0 did not show a checkpoint in the event log just before completion, but a different unit BETA_ beta26_ 00000058_ 0099_ 0-- (that finished seconds before 0376) did show a checkpoint just before completion:

09/08/2017 21:47:35 | World Community Grid | [checkpoint] result BETA_beta26_00000058_0099_0 checkpointed
09/08/2017 21:47:37 | World Community Grid | Message from task: 0
09/08/2017 21:47:38 | World Community Grid | Computation for task BETA_beta26_00000058_0099_0 finished

0099 showed a total of 9 checkpoints, also missing that after structure 1.

Unsure if it is useful as it wasn't on my machine, but a beta WUs that was able to download and run/complete on my machine (Mac) but failed on a Win and a linux.

BETA_beta26_00000056_1204
Opening Workunit Status and clicking Error for the Linux gets me this:
<core_client_version>7.6.31</core_client_version>
<![CDATA[
<message>
app_version download error: couldn't get input files:
<file_xfer_error>
<file_name>wcgrid_beta26_rosetta_7.10_x86_64-pc-linux-gnu</file_name>
<error_code>-224 (permanent HTTP error)</error_code>
<error_message>permanent HTTP error</error_message>
</file_xfer_error>
<file_xfer_error>
<file_name>beta26_image03_7.10.tga</file_name>
<error_code>-224 (permanent HTTP error)</error_code>
<error_message>permanent HTTP error</error_message>
</file_xfer_error>
<file_xfer_error>
<file_name>beta26_image04_7.10.tga</file_name>
<error_code>-224 (permanent HTTP error)</error_code>
<error_message>permanent HTTP error</error_message>
</file_xfer_error>
<file_xfer_error>
<file_name>beta26_image05_7.10.tga</file_name>
<error_code>-224 (permanent HTTP error)</error_code>
<error_message>permanent HTTP error</error_message>
</file_xfer_error>

</message>
]]>

And the same procedure for the Microsoft Windows 8.1 gets me:
<core_client_version>7.2.47</core_client_version>
<![CDATA[
<message>
app_version download error: couldn't get input files:
<file_xfer_error>
<file_name>wcgrid_beta26_rosetta_7.10_windows_intelx86</file_name>
<error_code>-224 (permanent HTTP error)</error_code>
<error_message>permanent HTTP error</error_message>
</file_xfer_error>
<file_xfer_error>
<file_name>wcgrid_beta26_gfx_7.10_windows_intelx86</file_name>
<error_code>-224 (permanent HTTP error)</error_code>
<error_message>permanent HTTP error</error_message>
</file_xfer_error>

</message>
]]>


Same deal with
BETA_beta26_00000058_0694
The windows box looks like the same client (OS Version is the same at Enterprise x64 Edition, (06.03.9600.00)) and the contents of the Error is the same.

On Windows Pro 8.1 (64 bits) :

Nom du résultat: BETA_ beta26_ 00000058_ 1952_ 0--
<core_client_version>7.6.33</core_client_version>
<![CDATA[
<message>
app_version download error: couldn't get input files:
<file_xfer_error>
<file_name>wcgrid_beta26_rosetta_7.10_windows_intelx86</file_name>
<error_code>-224 (permanent HTTP error)</error_code>
<error_message>permanent HTTP error</error_message>
</file_xfer_error>

</message>
]]>

We are still getting download errors (-224) and md5 hash errors (-119) on some of the beta WUs. These are happening with various BOINC client versions on both Windows and Mac.

Current results status view for beta:
~75 error (the 2 errors listed above)
~885 valid
~525 in progress