hobbitd_rrd error

My hobbit server has been error free since I installed 4.1.2 but in the
last day of so, has had an error for hobbitd_rrd .

The rrd-data.log shows:
*** glibc detected *** double linked list
Worker process died with exit code 134
*** glibc detected *** double free or corruption (fasttop)

I can't find anything in the archives about this. 

No changes made to the system, no client added. 
I;ves stopped and started hobbit with no changed.

The rrd graphs show gaps every 10 - 20 minutes or so.

Any suggestions? more data required?

Regards
Geoff


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