I have digital hygrometers that are more than 50% wrong. One never reads over 18% no matter the actual humidity. Cheap digital units (temp and hygrometers) with with resistive sensors they measure the electrical resistance at different humidity levels (and in the case of thermometers temperatures) this as you may have guessed is very small variations. That is the root of the issue. It is measuring very small variations and it takes very small flaws to make a difference. A bent cord, a bad solder joint on a board, the presence of contaminates on the surface of the sensor (dust, salts, urine...) even if a digital unit started accurate it can quickly change to inaccurate depending on what it has been exposed to. There are better digital units for both that are actually calibrated at the factory to insure scientific accuracy (traceable units) but they are usually very expensive (the unit I use in my professional life it over 1200$ and costs 300$ a year top re-certify)

The belief that a digital unit is more accurate than analogue is a myth. There are very accurate digital units and very accurate analogue units. (both hygrometers and thermometers) typically analogue units of equal accuracy are about 1/3 the price of the digital units. The real issue is how much accuracy do you actually need and how much accuracy are you willing to pay for with how much effort it takes.

I take this view. I want 1ºF up or down accuracy in temps and 5% up or down humidity. Most digital thermometers (like your accurite are rated to +/-2ºF and +/-10%RH) So a unit that is in this range is considered to be within an acceptable tolerance. Not all units are on the ends of that extreme but some might be. My thought is to buy the lowest priced digital thermometer with a probe you can find, but don't just get two get at least 3 and 5 would be better. (the last time I bought thermometers I found some on ebay for 1.20 shipped each I bought 15.) Lay them all out away from drafts and some where the temp is consistent wait 30 min and check them against each other many will basically be the same and a few will be quite different make the ones that are not (basically <half a degree>) the same and set them aside for parts or to get rid of (rehome repurpose toss) and use only the same reading ones. I re-check these every 6 months.

hygrometers I use an analogue 'hair' spring type they are robust as they are not bothered by dust much and read quickly. The things to look for in a good one are a metal face card (not cardboard like the reptile ones that often swell and jam the needle) and a calibration screw on the back. Hygrometers are easily tested (google salt test) and this type can be adjusted to read correctly if needed. Digital ones can be tested but few can be calibrated to read correct again, and often are inconsistent, and will not read the same error amount hours apart. (depends on the fault it has)

Personally I like the instrument to be correct but just make an educated guess to the humidity inside the enclosure. I place the hygrometer centrally in the enclosure and just figure the hides will be a few % different than the ambient (cool more hot less) and go from there.