A little search can explain the reason for inconstant records ""

Although a nationwide order was given in 1538 that each parish keep a register of baptisms, marriages, and burials, many parishes did not start to keep registers until later and some early records have since been lost or destroyed. The English Civil war caused turmoil and in some places entries to parish registers either ceased or entries became scarce lost or destroyed
Many records are damaged or missing and have to consider that the original records may not have been kept as well as they should have and are not ever going to be complete once we take into account the ravages of time Indeed only about 800 or so parishes have registers that survive back to an early date

If you enter Illegible in the surname search, in total there are 1,752 entries, 60 for Ruardean. Luckily, there are thousands transcribed with surnames.