Bluetooth headphones not working on my iPhone 16 Pro

[nucl30us_m]

I have 2 pairs of bluetooth headphones and neither is working consistently on my iPhone 16 Pro. They are the Sony WH-1000M5 and the Senheiser CX Plus True Wireless. They work intermittently for regular phone calls and music streaming, but they never work for calls on WhatsApp and Signal. And they only work sometimes for regular calls. They are paired and I have all the permissions enabled. It even shows the icon for the headphones when making a call, but then the sound goes through the phone's speaker. I've got the latest apps installed for the headphones, so I'm wondering why they're not working consistently. Has anyone else had an issue like this? I'd rather not buy airpods just to have something that works with iPhone, since these are both high quality items.