This happened in Wurm Unlimited, but for sure is also a bug in Wurm Online.
The Bug:
The bug is located in Item Class in the method fillTreasureChest().
There you can find the following line for spawning valrei items or items like the wand of seas and stuff like that, basicly tomes and other epic items.
valrei = 795 + Server.rand.nextInt(17);
Server.rand.nextInt(17) => This will do a random number from 0 to 16.
valrei = 795 + Server.rand.nextInt(17); // So this means you can receive items from 795 to 811 (template id) and the funny outcome is that 811 is the statue of horse only 795 to 810 are epic items, resulting into a very upset player Plus the bad side effect that only a GM can remove the statue.
The fix:
Change
valrei = 795 + Server.rand.nextInt(17);
to
valrei = 795 + Server.rand.nextInt(16);
Result: 1 of 100 bugs fixed so only 101 bugs in the code