Lookahead popping 2 contexts prevents pattern from repeating

[eugenesvk]

Example synax below consisting of 3 groups of elements with the 2nd either/or repeating:

1. name
2. optionally followed by properties (b=1) or arguments (just b). In general the key/arg names can be different, so I've made an equivalent regex b manually to force a branch point, and then I either match = or no = with a negative lookahead
3. ending with a ; or a newline terminator

Then I've noticed that the positive lookahead pops 2 contexts, which prevents the chain from continuing, so either manually changing that to 1 or adding an empty '' match fixes it But then this is totally unintuitive, I don't get why I need an empty match "dirtying" this clean conceptual rule.

Is there a way to make a 1 pop by the lookahead itself?

main : (~test   )* ;
test : 'name' (pprop | aarg)* ';|\n' ;
 pprop{variable.property          }   : ('b'{↓ re equiv to ⸙}     '='     '1');
 # aarg{ entity.other.attribute-name} : ('b'{↑ re equiv to ⸙}     '(?!=)'    ); # FAILS
 aarg{ entity.other.attribute-name}   : ('b'{↑ re equiv to ⸙}  '' '(?!=)'    ); # Works

Testing text, the fail appears by the rule stoping at the first b argument, refusing to go forward to match subsequent args/props

name b=1 b=1 b b b=1 b b=1 b b  ;
name b=1 b=1 b b b=1 b b=1 b b b=1;
name b b b=1 b b b b=1;