One often has to "coax" the propellant grains into ANY/ALL of the RMS cases, be it hobby line (18/20, 24/40, and 29/40-120) or the various 29-38-54-75-98mm HPR RMS cases. Often one has to peel part of the cardboard liner off the propellant grain to get it into the case. You are NOT experiencing anything abnormal.
Many new RMS users expect it to be a "Wham-Bam & you are done" experience in building RMS loads. It sometimes can be, but it is usually NOT so.
Some use a thin layer of "O-ring" grease on the outside liner of the propellant grain to get it into the casing also.
The key to RMS is in taking your time and following the directions EXACTLY.
If you don't follow the directions exactly the result is often a CATO !
When using copperheads, the easiest way is to use the special Aerotech "interlock" igniter clip, which is designed for them. The copperhead actually has two leads that are separated by a fine layer of plastic. It is a copper-plastic-copper sandwich. I use a lighter on the non-pyrogen coated end to melt the plastic....the two halves of copper curl away from each other...then one can use regular micro-clips.
When using copperheads (or ANY igniters for composite-propellant engines) you ABSOLUTELY CANNOT use a 4AA cell Estes-type "Electron Beam" controller to fire them....it WILL NOT RELIABLY WORK !
You MUST use a 12V car-battery power source type controller such as the Aerotech Interlock controller or the old Estes ASTRON launch controller. I personally have both & use both. One can also build their own 12V controller if they have the electrical experience.

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When in doubt, WHACK the GAS and DITCH the brake !!!

Yes, there is such a thing as NORMAL, if you have to ask what is "NORMAL" , you probably aren't !
Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY.
ALL systems are GO for MAYHEM, CHAOS, TURMOIL, FIASCOS, and HAVOC !