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I missed looking at this comment. Actually earlier I was running 4.3.14 on the SATA disk OS, but I upgraded to 5.1.4 (2 days ago and on this everything works well). On the new SSD disk OS, I have never installed 4.3.14 so I wonder why it's even appearing in the logs. I first installed 5.1.4 and then moved to 5.1.6 on the SSD. Earlier I was copying the vbox and vd files to move the VM, later when things started going wrong, then I exported the appliance as an ova 2.0 and then imported it. I don't get what you mean by "remove Version 4.3.14 r95030 and install the ones of your current VBox version.", actually I don't have any 4.3.14 stuff on this SSD system.

Guest additions are installed in the guest and where you will find you are running version 4.3.14. You need to remove those and install the ones for 5.1.6 since that is what you actually have installed as the main program.