Is Dizziness And Lightheadedness After Taking Carvedilol Normal?

I had a prescription refilled for my father two days ago for Carvefilol. He has been taking this medication, 25 mg twice daily for a number of years. However, the pill shape changed on the new refill from an oblong pill to a round pill shape (imprinted with ZC 42) and the new pill causes dizziness and light headed ness. The pharmacy has assured me that the new pill is the same medication - they re just using a new pharmaceutical company. Whats causing the reaction if its the same medication?