Generic vs. Name Brand Calan SR

My mother has been on Calan SR 240 mg for at least 15 years and her BP has always been well controlled. I checked her BP prior to recent doctor's appt. and found it to be very high. Re-checked it several times over 3-4 days and at the doctor's office and it was ruming in the range of 170-200/70-90; not her usual 120-130/70. While something in her general health may have changed, the only "new" piece in the equation is that we switched (late March/early April) to generic form. Have you heard of any incidents of this ?

We are going to switch back to name brand for 10 days before making other med adjustments.