This is a previously reported problem (TTSD-16799) that has usually been resolved with the current Service Packs.
The problem was reported with Tekla Structures 2017i SP4. The following ServicePack fix the problem: 2018 SP1, 2017 SP8, 2017i SPnext, 2016i SPnext
Make sure that you have installed the latest ServicePack for each version of Tekla Structures.
An overview of the current Service Pack can be found here:
If you still have a problem, the Tekla Forum is the place to go: