The front sight texture is missing on the following weapons when using the MRCO sight. The list is not exhaustive as I only noticed it on these weapons but haven't tested on all variants.
Updated:
MX 3GL 6.5 mm | arifle_MX_GL_F
MX 3GL 6.5 mm (Black) | arifle_MX_GL_Black_F
Katiba GL 6.5 mm | arifle_Katiba_GL_F
Sting 9 mm | SMG_02_F
PDW2000 9 mm | hgun_PDW2000_F {F26457} {F26458}
This issue has been reported in the past but has came up again in recent patches:
I loaded into the editor to test with other weapons and found that this issue also affects the Sting 9 mm and PDW2000 9 mm.
List of affected weapons and their classnames:
MX 3GL 6.5 mm | arifle_MX_GL_F
MX 3GL 6.5 mm (Black) | arifle_MX_GL_Black_F
Katiba GL 6.5 mm | arifle_Katiba_GL_F
Sting 9 mm | SMG_02_F
PDW2000 9 mm | hgun_PDW2000_F