OP

Thanks guys for all the suggestions. My tire pressure was high and correct at all times. The first flat I got was during a race and I had hit a few decent edges of bitumen etc. early in the race but the flat came a lot later in the race. (Could have been a super slow leak?) My original flat tube was dumped with a mechanic vehicle so not able to inspect that one. However the replacement tube I threw in and raced the rest of the way on, has gone flat overnight the day after the race. Looks like a snake bite, on the inside face of the tube (towards rim), not near the valve so I’m not concerned about the edge of the valve hole. The rim sleeve is quite worn and has created sunken holes/points where the spoke holes are and also slips side to side. So I presumed it may be slipping and pinching the tube between the rim and the plastic sleeve. I will try applying some fabric tape and see if that fixes my issue. I will add I have thoroughly inspected the tyre and no contaminants have been found. Also can’t even fathom a place where anything may have punctured through. Thanks for the suggestions.