When using the internal clock on your Cantar X as the master clock for setting up your Tentacle please make sure that you select in the menu Audio & Timecode Parameters -> Ltc level -> Medium. Any time the Cantar X is powered down you would need to re-sync the Tentacle.
That's why we recommend to work with external timecode and a Tentacle as master clock. Our Tentacles stay in sync for up to 24 hours after being synchronized at the start of the day. Their built-in batteries last even longer. If you connect a Tentacle to your Cantar X and select in the menu as Timecode source -> Ext. Clock you can power the Cantar X down without the need to re-sync afterwards.