Snom 710 reboot without apparently no reason

Hi all,

some users, suddently, have its SNOM 710 phones random reboot withount any apparently reason. They works flawlessy for years but, for some unknown reason, they started rebooting randomly every hour/hour and half. They run on the latest stable firmware available, 8.9.3.80. I've enabled remote syslog, just to see what's going on, and the latest messages recorded, before a random reboot, were:

[NOTICE] PHN: Config setup: found xml style settings
[NOTICE] PHN: last prov successful:1; uri: >http://XXXX/provisioning/snom.php?mac=$mac<; default uri: >http://provisioning.snom.com/snom710/snom710.php?mac={mac}<
[NOTICE] PHN: Fetching URL: https://admin:...@127.0.0.1:443/dummy.htm
[WARN  ] TLS: CertVerification for PhoneCtx disabled!
[NOTICE] CSTA: csta_cid = 2
phone_cid2
(reboot)
SYSLOG: Init snom 710 Version snom710-SIP 8.9.3.80
[DEBUG2] PHN: KMSG: <4>ifx_set_chip_number
[DEBUG2] PHN: KMSG: <4>ifx_set_base_address

Some months agoo we have a similar problem solved disabling LLCP (and it's still disabled on all our switches and phones). We have no idea of why some phones still rebooting and any help or suggestion were really appreciated.  Thanks.