VBoxHeadless eats 100% CPU even if guest OS is idle

[Miroslav Lachman]

We are using virtualbox-ose-kmod-5.2.22 and 
virtualbox-ose-nox11-5.2.22_1 on the FreeBSD 11.2-RELEASE-p7 amd64 host 
with 3 guests. 1 guest runs FreeBSD 11.2, 2 guests are Ubuntu mini.
Today I noticed 2 of 3 guests eat 100% CPU even if they are doing 
nothing. The FreeBSD guest is just IPSec gateway for two Ubuntu guests. 
If I enter the guest I see it is 99.9% idle.

# top in FreeBSD guest
27 processes:  1 running, 26 sleeping
CPU:  0.0% user,  0.0% nice,  0.0% system,  0.0% interrupt,  100% idle
Mem: 13M Active, 724M Inact, 12M Laundry, 194M Wired, 103M Buf, 22M Free

# top in FreeBSD host
CPU:  3.7% user,  0.0% nice, 14.7% system,  0.0% interrupt, 81.6% idle
Mem: 352M Active, 17G Inact, 315M Laundry, 5153M Wired, 1572M Buf, 951M Free
Swap: 16G Total, 59M Used, 16G Free

   PID USERNAME    THR PRI NICE   SIZE    RES STATE   C   TIME    WCPU 
COMMAND
   793 vboxusers    22  20    0  1161M  1081M select  0 969.0H 102.69% 
VBoxHeadless
  3878 vboxusers    20  20    0   672M   595M select  0 775.7H 101.44% 
VBoxHeadless


According to usage graphs this problem is there for about 40 days but 
host and all guest have uptime 61 days.

Each guest has 1 CPU, 768M RAM.

I found the exactly same problem on testing machine, FreeBSD 11.2 + 
VirtualBox 5.2.22 also. Just one guest doing nothing and VBoxHeadless 
eating 100% CPU.

Is it some know problem? Is there a way to fix / workaround it?

Is it fixed in newer version of VirtualBox? I never have this problem 
before.

Kind regards
Miroslav Lachman