Part (shown while opening assembly) disappears when assembly fully openend

Hi,

I took over an old assembly with most likely a lot of errors.

One problem I have is a neccessary Part (that is shown while opening assembly) disappears when assembly is fully openend.

It also is not shown in the parts tree or I can't find it in the hidden objects. What bugs me is, that it is shown when opening the assembly.

Example:

Assembly consists of:

   - Part1

   - Part2

   - Part3

While opening the Assembly all parts are shown: 1, 2 and 3. When the assembly finished loading, part2 is not shown anymore and also missing in the tree:

Assembly seems to consists of:

   - Part1

   - Part3

Where could I try to find the missing part?

Best regards,

Andrew

SolidworksModeling And Assemblies