Before continuing if you are reporting an issue, please ensure that all mods involved are updated to the latest version available, if your issue with with intermod compatibility such mixing C&B bits with other blocks make sure that MCMP is also updated. If your issue is a crash, be sure to include the crash log with your report.
When you place the blocks, theyre missing gaps in between them like when you have half blocks (slabs) and you place something above it and it floats, thats exactly whats happening. The blocks are not sticking together.

For any bug reports please provide the following details as well,

• MC Version: 1.16.4
• C&B Version: 0.3.4
• Do You have Optifine: