Slow Growing Spike Catyclia

[aussieboy]

I had a catyclia burdekin honey shona for about 2 years. It was already a flowering size when I bought it and I can say is very vigorous grower. Last year, I saw some small sheath growing in the middle on some of matured bulbs. However, they all get aborted for some reason. This year, I can see small sheaths forming again but looks like they are aborting again. Its been 4 weeks and the sheaths are not growing. I wonder if this is normal to get very slow growth of spike? Could it be bec. I often move the pot around and placed it on direct sun every morning? I havent own any Cattleya or hybrid other than this.