Melanie Griffith and Antonio Banderas
06/08/2014 at 03:00 PM EDT
Though Melanie Griffith
and Antonio Banderas
say they are divorcing "in a loving and friendly manner," sources connected to the couple suggest the romance wasn't always picture perfect.
Griffith, 56, filed for divorce
from Banderas, 53, on Friday after 18 years together. After their previous marriages fell apart, the actors met on the set of Too Much
in 1995, continuing to support each other's film careers for decades and raising their daughter Stella
Still, the partnership wasn't without its problems
"The split is not something new and out of the blue, they have had issues for years," a source close to Griffith tells PEOPLE. “The fights and separations got to be too much."
Banderas's globe-trotting career eventually took its toll, the source continues.
"He has always led an international life and during the times they were apart for business or film work, he began to live his own life away from her," the source says.
But another source friendly with both stars says they kept in close touch when they were apart. "They would talk on the phone four, five times a day," the source says. "They seemed to make it work."
And they always made the most of their reunions, spending downtime with their children in L.A. (Griffith is also mom to Fifty Shades of Grey
star Dakota Johnson, 24) and enjoying vacations at their home in Marbella, Spain.
"It's very sad," says the second source of the divorce news. "They had a solid relationship for so many years."
For much more on the couple's divorce, pick up the next issue of PEOPLE, on newsstands Friday.
Reporting by LINDA MARX and STEVE HELLING