Peterbilt 389 Power Steering building pressure and blowing fluid??

2018 Peterbilt 389/X15, started blowing fluid out cap. Flushed fluid and replaced internal filter. Operated ok for a bit then started doing it again. Replaced power steering pump and again new fluid/filter. Operated as should for a few days then started blowing fluid again. Contacted power steering pump manufacturer and they said must be steering box and agreed to send me a new pump to install with new steering box. Put on certified rebuilt steering box from Pete brand new not available for a while. New steering gear box, all new hoses, new power steering pump, new reservoir cap, new filter, and fluid. Operated nearly 250hrs flawlessly then started to blow fluid out cap again??? WTF. It will run fine for about an hour then puke fluid top it off and it might puke it out again or may run fine rest of the day. Puked it out twice today and I left it low didn’t top off and it finished out the day. Would whine a little during hard turns and now and then but overall operated ok. First time it puked fluid and I added or topped it off I looked in reservoir and fluid is not foaming. No leaks, not sucking air. Got me stumped? Anyone had this issue or have any idea what is going on? Any help would be greatly appreciated. Thank you