If a creature has multiple instances of modular, each one works separately.
October 5, 2018 · Guilds of Ravnica
Sunburst adds counters only if the object with sunburst is entering the battlefield from the stack as a resolving spell and only if one or more colored mana was spent on its costs, including additional or alternative costs.
July 13, 2013 · Magic 2014
Sunburst applies only as the spell is resolving and only if one or more colored mana was spent on its costs. Mana paid for additional or alternative costs applies.
June 17, 2011 · Commander 2011
If a creature has multiple instances of bushido, each triggers separately.
February 1, 2010 · Worldwake
If a permanent has multiple instances of soulshift, each triggers separately.