When saving an assembly as JT and then opening it with JT2GO (or another viewer) components which contain an assembly feature will have their original file name changed - adding the suffix "oa" and a sequential number.
In this example, we see in Solid Edge the names of the components: Part1 (containing an assembly feature) and Part2 (with no assembly feature). The assembly is then saved as a JT.
Opening the saved JT file with JT2GO you can see the name of Part1 has changed:
Solution
This is working as designed.
When an assembly containing an assembly feature is converted to JT, you need to be aware that the original part in the assembly file is different than the one shown in the JT file, since in JT, the assembly feature is seen as feature of the part itself. Consequently the suffix "oa_0" is added.
Hardware/Software Configuration
Platform: all
OS: n/a
OS Version: n/a
Product: SOLID_EDGE
Application: TRANSLATORS
Version: V220.0
Function: JT
Ref: 002-8014804